From patchwork Sat Jun 29 08:43:27 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: KP Singh X-Patchwork-Id: 13716843 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 103699445; Sat, 29 Jun 2024 08:43:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650621; cv=none; b=sAFG1p1duJuQs1AowXJSbFI7nT84KqWSfZovdKxJSVL04xqIJ56fPnX7R934t8whgD0Am8nAijqmG7du7p4nHQYsKnf7a11yMzgfkClyywAsFUfKcWJLOYW3RxbcLBLJYmWqFov9YnktQ7zh9O7jqdFJwo7WZC1K3w8E1eCPiRc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650621; c=relaxed/simple; bh=hzkTRNL0yH8hJQz0aQmeB/BDH18/T05HKiqAEZXYhFE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FxX+8G1/31F/1IGCU0Mp7onH71rCRtcqM33oKMhz7/rQGY40ANLDYZ5azJpmQ4XOW8V5exhFgqQQ4gLbTJ4MQc5dOPpP1DpHFWL3wAT+jpXYoprTSJFDfIG/Lfvsdx3FPwlevv5oYwLa/KCpeUXcRn9q404UFtPO5yuSgMEWpWM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jfG6YnWO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jfG6YnWO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E267C4AF07; Sat, 29 Jun 2024 08:43:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719650620; bh=hzkTRNL0yH8hJQz0aQmeB/BDH18/T05HKiqAEZXYhFE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jfG6YnWO1ltBZyckuEaT8L66oYYmDHFd465wvGolNanGeptTTJl5Jv2UYgq6a59AL O+awJ6x8Lcy7bgXdYnhN7Bdt8jIN6jWt5Qp8MTj2xWgNA2KOWjdufXAmMXcwUmgt0E V2OWkZ6ZDJ3E6T6cjJEg+bi2DpKRykQZBehu1j17Pkt22ACJw8ufHaxpZB8b1QD4I4 9DnjapOMcPEJDrSx4I0JO/qH8S3sI2Kfrw0VU+uqxxw5zYIRIp6UvWxyBa/kHi+Jwg iLVqiJBN53EEXtEOYcYtm6gBmtIQDYWQfUglkw7P+WCBB6trelu7rHuLxU56CI+0s1 YYn+r//YHZiww== From: KP Singh To: linux-security-module@vger.kernel.org, bpf@vger.kernel.org Cc: ast@kernel.org, paul@paul-moore.com, casey@schaufler-ca.com, andrii@kernel.org, keescook@chromium.org, daniel@iogearbox.net, renauld@google.com, revest@chromium.org, song@kernel.org, KP Singh Subject: [PATCH v13 1/5] kernel: Add helper macros for loop unrolling Date: Sat, 29 Jun 2024 10:43:27 +0200 Message-ID: <20240629084331.3807368-2-kpsingh@kernel.org> X-Mailer: git-send-email 2.45.2.803.g4e1b14247a-goog In-Reply-To: <20240629084331.3807368-1-kpsingh@kernel.org> References: <20240629084331.3807368-1-kpsingh@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This helps in easily initializing blocks of code (e.g. static calls and keys). UNROLL(N, MACRO, __VA_ARGS__) calls MACRO N times with the first argument as the index of the iteration. This allows string pasting to create unique tokens for variable names, function calls etc. As an example: #include #define MACRO(N, a, b) \ int add_##N(int a, int b) \ { \ return a + b + N; \ } UNROLL(2, MACRO, x, y) expands to: int add_0(int x, int y) { return x + y + 0; } int add_1(int x, int y) { return x + y + 1; } Reviewed-by: Kees Cook Reviewed-by: Casey Schaufler Acked-by: Song Liu Acked-by: Andrii Nakryiko Signed-off-by: KP Singh --- include/linux/unroll.h | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) create mode 100644 include/linux/unroll.h diff --git a/include/linux/unroll.h b/include/linux/unroll.h new file mode 100644 index 000000000000..d42fd6366373 --- /dev/null +++ b/include/linux/unroll.h @@ -0,0 +1,36 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +/* + * Copyright (C) 2023 Google LLC. + */ + +#ifndef __UNROLL_H +#define __UNROLL_H + +#include + +#define UNROLL(N, MACRO, args...) CONCATENATE(__UNROLL_, N)(MACRO, args) + +#define __UNROLL_0(MACRO, args...) +#define __UNROLL_1(MACRO, args...) __UNROLL_0(MACRO, args) MACRO(0, args) +#define __UNROLL_2(MACRO, args...) __UNROLL_1(MACRO, args) MACRO(1, args) +#define __UNROLL_3(MACRO, args...) __UNROLL_2(MACRO, args) MACRO(2, args) +#define __UNROLL_4(MACRO, args...) __UNROLL_3(MACRO, args) MACRO(3, args) +#define __UNROLL_5(MACRO, args...) __UNROLL_4(MACRO, args) MACRO(4, args) +#define __UNROLL_6(MACRO, args...) __UNROLL_5(MACRO, args) MACRO(5, args) +#define __UNROLL_7(MACRO, args...) __UNROLL_6(MACRO, args) MACRO(6, args) +#define __UNROLL_8(MACRO, args...) __UNROLL_7(MACRO, args) MACRO(7, args) +#define __UNROLL_9(MACRO, args...) __UNROLL_8(MACRO, args) MACRO(8, args) +#define __UNROLL_10(MACRO, args...) __UNROLL_9(MACRO, args) MACRO(9, args) +#define __UNROLL_11(MACRO, args...) __UNROLL_10(MACRO, args) MACRO(10, args) +#define __UNROLL_12(MACRO, args...) __UNROLL_11(MACRO, args) MACRO(11, args) +#define __UNROLL_13(MACRO, args...) __UNROLL_12(MACRO, args) MACRO(12, args) +#define __UNROLL_14(MACRO, args...) __UNROLL_13(MACRO, args) MACRO(13, args) +#define __UNROLL_15(MACRO, args...) __UNROLL_14(MACRO, args) MACRO(14, args) +#define __UNROLL_16(MACRO, args...) __UNROLL_15(MACRO, args) MACRO(15, args) +#define __UNROLL_17(MACRO, args...) __UNROLL_16(MACRO, args) MACRO(16, args) +#define __UNROLL_18(MACRO, args...) __UNROLL_17(MACRO, args) MACRO(17, args) +#define __UNROLL_19(MACRO, args...) __UNROLL_18(MACRO, args) MACRO(18, args) +#define __UNROLL_20(MACRO, args...) __UNROLL_19(MACRO, args) MACRO(19, args) + +#endif /* __UNROLL_H */ From patchwork Sat Jun 29 08:43:28 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: KP Singh X-Patchwork-Id: 13716844 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BB9C69445; Sat, 29 Jun 2024 08:43:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650623; cv=none; b=Fj6xUziZA540qTsEZPcgJOvnpaTrZdNhOYzZ7tqxgcQyzRkcLAXvpCPc3k6uV74Mvw9fM1/Cd9pz3j4mq7OrbH2pvlsF3eoEK2cPYkeDen7LFJeLjIcFqtB2xFGfebbiVXeU1gBTWyGR2fovVmnHKOtWOseZbPUu+IH5DN6Zhgw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650623; c=relaxed/simple; bh=4ghV88tVxr7Utx3+qpEzRMktsglvgk1QVmjp8gqfrgY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ExKA8uyD8MtDrnHzTpAA0LjtD31moN0RnXurIAMASme0uZ0pg1Qw7VqlZ92meT1bPREseeeFYj7GK3wiwezAb5wJpFze0H/FSfs8b6IEowBZpMpOkFFI3b+edNQ4sEB4ZiG3oFs1M4a0QHi/q9RrrCqPut5DcO/mV3s7ebl7+6U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AWvbfphw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AWvbfphw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EED09C4AF09; Sat, 29 Jun 2024 08:43:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719650623; bh=4ghV88tVxr7Utx3+qpEzRMktsglvgk1QVmjp8gqfrgY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AWvbfphwR43wcXdeHkwyOHBEPrqFL9RbhslpjrNMBCS1msamVQ3NDnOkDODz4ojjC 6q1FN31StWVQVdUcm+nDcxZUMeHK4JPEKfQzIF/4T2tIJjlc9bza5Jge9UesMQauyM mU8psDGpZ1BMMvVQ5mNu5re5i3Lb8XdXrVmjcIVWfqrDNW0O+pjNaV/eQhvjK/f0pP Acvb3f+YHTN4fnJKuc/13B0l7MhQwXDcMgUF4seWXYw5IIxwAfQtcRYVAXOvX53veA PB0AtEohH73+/DNgH6qRi2IEYfZBENaeZedQMwworu4tgriHIl812VzVAeJnv2jQ7S Tecm7UNE+r1SQ== From: KP Singh To: linux-security-module@vger.kernel.org, bpf@vger.kernel.org Cc: ast@kernel.org, paul@paul-moore.com, casey@schaufler-ca.com, andrii@kernel.org, keescook@chromium.org, daniel@iogearbox.net, renauld@google.com, revest@chromium.org, song@kernel.org, Kui-Feng Lee , KP Singh Subject: [PATCH v13 2/5] security: Count the LSMs enabled at compile time Date: Sat, 29 Jun 2024 10:43:28 +0200 Message-ID: <20240629084331.3807368-3-kpsingh@kernel.org> X-Mailer: git-send-email 2.45.2.803.g4e1b14247a-goog In-Reply-To: <20240629084331.3807368-1-kpsingh@kernel.org> References: <20240629084331.3807368-1-kpsingh@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 These macros are a clever trick to determine a count of the number of LSMs that are enabled in the config to ascertain the maximum number of static calls that need to be configured per LSM hook. Without this one would need to generate static calls for the total number of LSMs in the kernel (even if they are not compiled) times the number of LSM hooks which ends up being quite wasteful. Suggested-by: Kui-Feng Lee Suggested-by: Andrii Nakryiko Acked-by: Song Liu Acked-by: Andrii Nakryiko Reviewed-by: Kees Cook Reviewed-by: Casey Schaufler Signed-off-by: KP Singh --- include/linux/args.h | 6 +- include/linux/lsm_count.h | 128 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 131 insertions(+), 3 deletions(-) create mode 100644 include/linux/lsm_count.h diff --git a/include/linux/args.h b/include/linux/args.h index 8ff60a54eb7d..2e8e65d975c7 100644 --- a/include/linux/args.h +++ b/include/linux/args.h @@ -17,9 +17,9 @@ * that as _n. */ -/* This counts to 12. Any more, it will return 13th argument. */ -#define __COUNT_ARGS(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _n, X...) _n -#define COUNT_ARGS(X...) __COUNT_ARGS(, ##X, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) +/* This counts to 15. Any more, it will return 16th argument. */ +#define __COUNT_ARGS(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _n, X...) _n +#define COUNT_ARGS(X...) __COUNT_ARGS(, ##X, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) /* Concatenate two parameters, but allow them to be expanded beforehand. */ #define __CONCAT(a, b) a ## b diff --git a/include/linux/lsm_count.h b/include/linux/lsm_count.h new file mode 100644 index 000000000000..73c7cc81349b --- /dev/null +++ b/include/linux/lsm_count.h @@ -0,0 +1,128 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +/* + * Copyright (C) 2023 Google LLC. + */ + +#ifndef __LINUX_LSM_COUNT_H +#define __LINUX_LSM_COUNT_H + +#include + +#ifdef CONFIG_SECURITY + +/* + * Macros to count the number of LSMs enabled in the kernel at compile time. + */ + +/* + * Capabilities is enabled when CONFIG_SECURITY is enabled. + */ +#if IS_ENABLED(CONFIG_SECURITY) +#define CAPABILITIES_ENABLED 1, +#else +#define CAPABILITIES_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_SELINUX) +#define SELINUX_ENABLED 1, +#else +#define SELINUX_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_SMACK) +#define SMACK_ENABLED 1, +#else +#define SMACK_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_APPARMOR) +#define APPARMOR_ENABLED 1, +#else +#define APPARMOR_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_TOMOYO) +#define TOMOYO_ENABLED 1, +#else +#define TOMOYO_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_YAMA) +#define YAMA_ENABLED 1, +#else +#define YAMA_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_LOADPIN) +#define LOADPIN_ENABLED 1, +#else +#define LOADPIN_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_LOCKDOWN_LSM) +#define LOCKDOWN_ENABLED 1, +#else +#define LOCKDOWN_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_SAFESETID) +#define SAFESETID_ENABLED 1, +#else +#define SAFESETID_ENABLED +#endif + +#if IS_ENABLED(CONFIG_BPF_LSM) +#define BPF_LSM_ENABLED 1, +#else +#define BPF_LSM_ENABLED +#endif + +#if IS_ENABLED(CONFIG_SECURITY_LANDLOCK) +#define LANDLOCK_ENABLED 1, +#else +#define LANDLOCK_ENABLED +#endif + +#if IS_ENABLED(CONFIG_IMA) +#define IMA_ENABLED 1, +#else +#define IMA_ENABLED +#endif + +#if IS_ENABLED(CONFIG_EVM) +#define EVM_ENABLED 1, +#else +#define EVM_ENABLED +#endif + +/* + * There is a trailing comma that we need to be accounted for. This is done by + * using a skipped argument in __COUNT_LSMS + */ +#define __COUNT_LSMS(skipped_arg, args...) COUNT_ARGS(args...) +#define COUNT_LSMS(args...) __COUNT_LSMS(args) + +#define MAX_LSM_COUNT \ + COUNT_LSMS( \ + CAPABILITIES_ENABLED \ + SELINUX_ENABLED \ + SMACK_ENABLED \ + APPARMOR_ENABLED \ + TOMOYO_ENABLED \ + YAMA_ENABLED \ + LOADPIN_ENABLED \ + LOCKDOWN_ENABLED \ + SAFESETID_ENABLED \ + BPF_LSM_ENABLED \ + LANDLOCK_ENABLED \ + IMA_ENABLED \ + EVM_ENABLED) + +#else + +#define MAX_LSM_COUNT 0 + +#endif /* CONFIG_SECURITY */ + +#endif /* __LINUX_LSM_COUNT_H */ From patchwork Sat Jun 29 08:43:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: KP Singh X-Patchwork-Id: 13716845 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 740CD9445; Sat, 29 Jun 2024 08:43:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650626; cv=none; b=aH5Ajc+mOC9WIS4cPUPGheo9UR97780kk2Jl8PkoihWm3Px4+qYiHifq8fJ6YE3P7GSH/f7EnhKluvON7ANQnV80sDVKHr9mTmlI+Tvm8ln0ZYvt8izRCsQSTvGHvpc+4pd+1zh91NiqU3iO5VDpAuyHmJChSc7H0ZMIMWsKs5c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650626; c=relaxed/simple; bh=qawJj4YIfVzlRKmuEAMjQvpTbBfQC8XIU3jLEPkN36U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iAuZHeVzgWmBKhW/wzYjew/h1ALoVTZNQ6Z8wzn0gTu54Yx5IpRK3u0Juv4nVAE9PgeBUXMDns7V4aacIs593lZ85E0mO0V94hbuCwVivOYV4hWt5+7LKgZc7vKnxRLI0v5v9kEKuh66s4iEjbSwfQPBb+042aZkq+IBDukrjLE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=D39gI0bE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="D39gI0bE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A169AC4AF07; Sat, 29 Jun 2024 08:43:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719650625; bh=qawJj4YIfVzlRKmuEAMjQvpTbBfQC8XIU3jLEPkN36U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D39gI0bE3syCoYn4+H9V2mTrNK9niUeajrAdcgrcrb8KzzX4apk11vJ73BefS96sX qQBx1urfXifIc4EcOT4bFzaTKnSfMdee4ns76rjUELuO5d0p+EQpNdwwthPvebyWUF gabKVlLtGZJ+o96LQiuC4Vhn+ywEAK5XKIE2nkioeXY31VtuD50WJdyge+1PXS7oZS PDnbVQfNvxICGyEFTqCZ85MqowMgzlKwDtW7etQK4Ozo/TjlVBIbvf4MBue/4FnoNo mET/D3T4BesCwr5Ji2mQW8bXJ/ajkonR0dgTgeOfe6nP+PuFzK2jfsbGiSL/rZCSYA cKZNDaYSkCFgA== From: KP Singh To: linux-security-module@vger.kernel.org, bpf@vger.kernel.org Cc: ast@kernel.org, paul@paul-moore.com, casey@schaufler-ca.com, andrii@kernel.org, keescook@chromium.org, daniel@iogearbox.net, renauld@google.com, revest@chromium.org, song@kernel.org, KP Singh Subject: [PATCH v13 3/5] security: Replace indirect LSM hook calls with static calls Date: Sat, 29 Jun 2024 10:43:29 +0200 Message-ID: <20240629084331.3807368-4-kpsingh@kernel.org> X-Mailer: git-send-email 2.45.2.803.g4e1b14247a-goog In-Reply-To: <20240629084331.3807368-1-kpsingh@kernel.org> References: <20240629084331.3807368-1-kpsingh@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 LSM hooks are currently invoked from a linked list as indirect calls which are invoked using retpolines as a mitigation for speculative attacks (Branch History / Target injection) and add extra overhead which is especially bad in kernel hot paths: security_file_ioctl: 0xff...0320 <+0>: endbr64 0xff...0324 <+4>: push %rbp 0xff...0325 <+5>: push %r15 0xff...0327 <+7>: push %r14 0xff...0329 <+9>: push %rbx 0xff...032a <+10>: mov %rdx,%rbx 0xff...032d <+13>: mov %esi,%ebp 0xff...032f <+15>: mov %rdi,%r14 0xff...0332 <+18>: mov $0xff...7030,%r15 0xff...0339 <+25>: mov (%r15),%r15 0xff...033c <+28>: test %r15,%r15 0xff...033f <+31>: je 0xff...0358 0xff...0341 <+33>: mov 0x18(%r15),%r11 0xff...0345 <+37>: mov %r14,%rdi 0xff...0348 <+40>: mov %ebp,%esi 0xff...034a <+42>: mov %rbx,%rdx 0xff...034d <+45>: call 0xff...2e0 <__x86_indirect_thunk_array+352> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Indirect calls that use retpolines leading to overhead, not just due to extra instruction but also branch misses. 0xff...0352 <+50>: test %eax,%eax 0xff...0354 <+52>: je 0xff...0339 0xff...0356 <+54>: jmp 0xff...035a 0xff...0358 <+56>: xor %eax,%eax 0xff...035a <+58>: pop %rbx 0xff...035b <+59>: pop %r14 0xff...035d <+61>: pop %r15 0xff...035f <+63>: pop %rbp 0xff...0360 <+64>: jmp 0xff...47c4 <__x86_return_thunk> The indirect calls are not really needed as one knows the addresses of enabled LSM callbacks at boot time and only the order can possibly change at boot time with the lsm= kernel command line parameter. An array of static calls is defined per LSM hook and the static calls are updated at boot time once the order has been determined. A static key guards whether an LSM static call is enabled or not, without this static key, for LSM hooks that return an int, the presence of the hook that returns a default value can create side-effects which has resulted in bugs [1]. With the hook now exposed as a static call, one can see that the retpolines are no longer there and the LSM callbacks are invoked directly: security_file_ioctl: 0xff...0ca0 <+0>: endbr64 0xff...0ca4 <+4>: nopl 0x0(%rax,%rax,1) 0xff...0ca9 <+9>: push %rbp 0xff...0caa <+10>: push %r14 0xff...0cac <+12>: push %rbx 0xff...0cad <+13>: mov %rdx,%rbx 0xff...0cb0 <+16>: mov %esi,%ebp 0xff...0cb2 <+18>: mov %rdi,%r14 0xff...0cb5 <+21>: jmp 0xff...0cc7 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Static key enabled for SELinux 0xffffffff818f0cb7 <+23>: jmp 0xff...0cde ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Static key enabled for BPF LSM. This is something that is changed to default to false to avoid the existing side effect issues of BPF LSM [1] in a subsequent patch. 0xff...0cb9 <+25>: xor %eax,%eax 0xff...0cbb <+27>: xchg %ax,%ax 0xff...0cbd <+29>: pop %rbx 0xff...0cbe <+30>: pop %r14 0xff...0cc0 <+32>: pop %rbp 0xff...0cc1 <+33>: cs jmp 0xff...0000 <__x86_return_thunk> 0xff...0cc7 <+39>: endbr64 0xff...0ccb <+43>: mov %r14,%rdi 0xff...0cce <+46>: mov %ebp,%esi 0xff...0cd0 <+48>: mov %rbx,%rdx 0xff...0cd3 <+51>: call 0xff...3230 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Direct call to SELinux. 0xff...0cd8 <+56>: test %eax,%eax 0xff...0cda <+58>: jne 0xff...0cbd 0xff...0cdc <+60>: jmp 0xff...0cb7 0xff...0cde <+62>: endbr64 0xff...0ce2 <+66>: mov %r14,%rdi 0xff...0ce5 <+69>: mov %ebp,%esi 0xff...0ce7 <+71>: mov %rbx,%rdx 0xff...0cea <+74>: call 0xff...e220 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Direct call to BPF LSM. 0xff...0cef <+79>: test %eax,%eax 0xff...0cf1 <+81>: jne 0xff...0cbd 0xff...0cf3 <+83>: jmp 0xff...0cb9 0xff...0cf5 <+85>: endbr64 0xff...0cf9 <+89>: mov %r14,%rdi 0xff...0cfc <+92>: mov %ebp,%esi 0xff...0cfe <+94>: mov %rbx,%rdx 0xff...0d01 <+97>: pop %rbx 0xff...0d02 <+98>: pop %r14 0xff...0d04 <+100>: pop %rbp 0xff...0d05 <+101>: ret 0xff...0d06 <+102>: int3 0xff...0d07 <+103>: int3 0xff...0d08 <+104>: int3 0xff...0d09 <+105>: int3 While this patch uses static_branch_unlikely indicating that an LSM hook is likely to be not present. In most cases this is still a better choice as even when an LSM with one hook is added, empty slots are created for all LSM hooks (especially when many LSMs that do not initialize most hooks are present on the system). There are some hooks that don't use the call_int_hook and call_void_hook. These hooks are updated to use a new macro called lsm_for_each_hook where the lsm_callback is directly invoked as an indirect call. These are updated in a subsequent patch to also use static calls. Below are results of the relevant Unixbench system benchmarks with BPF LSM and SELinux enabled with default policies enabled with and without these patches. Benchmark Delta(%): (+ is better) =============================================================================== Execl Throughput +1.9356 File Write 1024 bufsize 2000 maxblocks +6.5953 Pipe Throughput +9.5499 Pipe-based Context Switching +3.0209 Process Creation +2.3246 Shell Scripts (1 concurrent) +1.4975 System Call Overhead +2.7815 System Benchmarks Index Score (Partial Only): +3.4859 In the best case, some syscalls like eventfd_create benefitted to about ~10%. [1] https://lore.kernel.org/linux-security-module/20220609234601.2026362-1-kpsingh@kernel.org/ Reviewed-by: Casey Schaufler Reviewed-by: Kees Cook Acked-by: Song Liu Acked-by: Andrii Nakryiko Signed-off-by: KP Singh --- include/linux/lsm_hooks.h | 72 ++++++++++++-- security/security.c | 198 ++++++++++++++++++++++++++------------ 2 files changed, 197 insertions(+), 73 deletions(-) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index efd4a0655159..a66ca68485a2 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -30,19 +30,66 @@ #include #include #include +#include +#include +#include +#include + +#define SECURITY_HOOK_ACTIVE_KEY(HOOK, IDX) security_hook_active_##HOOK##_##IDX + +/* + * Identifier for the LSM static calls. + * HOOK is an LSM hook as defined in linux/lsm_hookdefs.h + * IDX is the index of the static call. 0 <= NUM < MAX_LSM_COUNT + */ +#define LSM_STATIC_CALL(HOOK, IDX) lsm_static_call_##HOOK##_##IDX + +/* + * Call the macro M for each LSM hook MAX_LSM_COUNT times. + */ +#define LSM_LOOP_UNROLL(M, ...) \ +do { \ + UNROLL(MAX_LSM_COUNT, M, __VA_ARGS__) \ +} while (0) + +#define LSM_DEFINE_UNROLL(M, ...) UNROLL(MAX_LSM_COUNT, M, __VA_ARGS__) union security_list_options { #define LSM_HOOK(RET, DEFAULT, NAME, ...) RET (*NAME)(__VA_ARGS__); #include "lsm_hook_defs.h" #undef LSM_HOOK + void *lsm_func_addr; }; -struct security_hook_heads { - #define LSM_HOOK(RET, DEFAULT, NAME, ...) struct hlist_head NAME; - #include "lsm_hook_defs.h" - #undef LSM_HOOK +/* + * @key: static call key as defined by STATIC_CALL_KEY + * @trampoline: static call trampoline as defined by STATIC_CALL_TRAMP + * @hl: The security_hook_list as initialized by the owning LSM. + * @active: Enabled when the static call has an LSM hook associated. + */ +struct lsm_static_call { + struct static_call_key *key; + void *trampoline; + struct security_hook_list *hl; + /* this needs to be true or false based on what the key defaults to */ + struct static_key_false *active; } __randomize_layout; +/* + * Table of the static calls for each LSM hook. + * Once the LSMs are initialized, their callbacks will be copied to these + * tables such that the calls are filled backwards (from last to first). + * This way, we can jump directly to the first used static call, and execute + * all of them after. This essentially makes the entry point + * dynamic to adapt the number of static calls to the number of callbacks. + */ +struct lsm_static_calls_table { + #define LSM_HOOK(RET, DEFAULT, NAME, ...) \ + struct lsm_static_call NAME[MAX_LSM_COUNT]; + #include + #undef LSM_HOOK +} __packed __randomize_layout; + /** * struct lsm_id - Identify a Linux Security Module. * @lsm: name of the LSM, must be approved by the LSM maintainers @@ -58,10 +105,14 @@ struct lsm_id { /* * Security module hook list structure. * For use with generic list macros for common operations. + * + * struct security_hook_list - Contents of a cacheable, mappable object. + * @scalls: The beginning of the array of static calls assigned to this hook. + * @hook: The callback for the hook. + * @lsm: The name of the lsm that owns this hook. */ struct security_hook_list { - struct hlist_node list; - struct hlist_head *head; + struct lsm_static_call *scalls; union security_list_options hook; const struct lsm_id *lsmid; } __randomize_layout; @@ -111,10 +162,12 @@ static inline struct xattr *lsm_get_xattr_slot(struct xattr *xattrs, * care of the common case and reduces the amount of * text involved. */ -#define LSM_HOOK_INIT(HEAD, HOOK) \ - { .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } } +#define LSM_HOOK_INIT(NAME, HOOK) \ + { \ + .scalls = static_calls_table.NAME, \ + .hook = { .NAME = HOOK } \ + } -extern struct security_hook_heads security_hook_heads; extern char *lsm_names; extern void security_add_hooks(struct security_hook_list *hooks, int count, @@ -152,5 +205,6 @@ extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[]; __aligned(sizeof(unsigned long)) extern int lsm_inode_alloc(struct inode *inode); +extern struct lsm_static_calls_table static_calls_table __ro_after_init; #endif /* ! __LINUX_LSM_HOOKS_H */ diff --git a/security/security.c b/security/security.c index 9c3fb2f60e2a..e0ec185cf125 100644 --- a/security/security.c +++ b/security/security.c @@ -30,6 +30,8 @@ #include #include #include +#include +#include /* How many LSMs were built into the kernel? */ #define LSM_COUNT (__end_lsm_info - __start_lsm_info) @@ -93,7 +95,6 @@ const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX + 1] = { [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -struct security_hook_heads security_hook_heads __ro_after_init; static BLOCKING_NOTIFIER_HEAD(blocking_lsm_notifier_chain); static struct kmem_cache *lsm_file_cache; @@ -112,6 +113,51 @@ static __initconst const char *const builtin_lsm_order = CONFIG_LSM; static __initdata struct lsm_info **ordered_lsms; static __initdata struct lsm_info *exclusive; + +#ifdef CONFIG_HAVE_STATIC_CALL +#define LSM_HOOK_TRAMP(NAME, NUM) \ + &STATIC_CALL_TRAMP(LSM_STATIC_CALL(NAME, NUM)) +#else +#define LSM_HOOK_TRAMP(NAME, NUM) NULL +#endif + +/* + * Define static calls and static keys for each LSM hook. + */ + +#define DEFINE_LSM_STATIC_CALL(NUM, NAME, RET, ...) \ + DEFINE_STATIC_CALL_NULL(LSM_STATIC_CALL(NAME, NUM), \ + *((RET(*)(__VA_ARGS__))NULL)); \ + DEFINE_STATIC_KEY_FALSE(SECURITY_HOOK_ACTIVE_KEY(NAME, NUM)); + +#define LSM_HOOK(RET, DEFAULT, NAME, ...) \ + LSM_DEFINE_UNROLL(DEFINE_LSM_STATIC_CALL, NAME, RET, __VA_ARGS__) +#include +#undef LSM_HOOK +#undef DEFINE_LSM_STATIC_CALL + +/* + * Initialise a table of static calls for each LSM hook. + * DEFINE_STATIC_CALL_NULL invocation above generates a key (STATIC_CALL_KEY) + * and a trampoline (STATIC_CALL_TRAMP) which are used to call + * __static_call_update when updating the static call. + */ +struct lsm_static_calls_table static_calls_table __ro_after_init = { +#define INIT_LSM_STATIC_CALL(NUM, NAME) \ + (struct lsm_static_call) { \ + .key = &STATIC_CALL_KEY(LSM_STATIC_CALL(NAME, NUM)), \ + .trampoline = LSM_HOOK_TRAMP(NAME, NUM), \ + .active = &SECURITY_HOOK_ACTIVE_KEY(NAME, NUM), \ + }, +#define LSM_HOOK(RET, DEFAULT, NAME, ...) \ + .NAME = { \ + LSM_DEFINE_UNROLL(INIT_LSM_STATIC_CALL, NAME) \ + }, +#include +#undef LSM_HOOK +#undef INIT_LSM_STATIC_CALL +}; + static __initdata bool debug; #define init_debug(...) \ do { \ @@ -172,7 +218,7 @@ static void __init append_ordered_lsm(struct lsm_info *lsm, const char *from) if (exists_ordered_lsm(lsm)) return; - if (WARN(last_lsm == LSM_COUNT, "%s: out of LSM slots!?\n", from)) + if (WARN(last_lsm == LSM_COUNT, "%s: out of LSM static calls!?\n", from)) return; /* Enable this LSM, if it is not already set. */ @@ -352,6 +398,25 @@ static void __init ordered_lsm_parse(const char *order, const char *origin) kfree(sep); } +static void __init lsm_static_call_init(struct security_hook_list *hl) +{ + struct lsm_static_call *scall = hl->scalls; + int i; + + for (i = 0; i < MAX_LSM_COUNT; i++) { + /* Update the first static call that is not used yet */ + if (!scall->hl) { + __static_call_update(scall->key, scall->trampoline, + hl->hook.lsm_func_addr); + scall->hl = hl; + static_branch_enable(scall->active); + return; + } + scall++; + } + panic("%s - Ran out of static slots.\n", __func__); +} + static void __init lsm_early_cred(struct cred *cred); static void __init lsm_early_task(struct task_struct *task); @@ -432,11 +497,6 @@ int __init early_security_init(void) { struct lsm_info *lsm; -#define LSM_HOOK(RET, DEFAULT, NAME, ...) \ - INIT_HLIST_HEAD(&security_hook_heads.NAME); -#include "linux/lsm_hook_defs.h" -#undef LSM_HOOK - for (lsm = __start_early_lsm_info; lsm < __end_early_lsm_info; lsm++) { if (!lsm->enabled) lsm->enabled = &lsm_enabled_true; @@ -564,7 +624,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count, for (i = 0; i < count; i++) { hooks[i].lsmid = lsmid; - hlist_add_tail_rcu(&hooks[i].list, hooks[i].head); + lsm_static_call_init(&hooks[i]); } /* @@ -856,29 +916,43 @@ int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, u32 *uctx_len, * call_int_hook: * This is a hook that returns a value. */ +#define __CALL_STATIC_VOID(NUM, HOOK, ...) \ +do { \ + if (static_branch_unlikely(&SECURITY_HOOK_ACTIVE_KEY(HOOK, NUM))) { \ + static_call(LSM_STATIC_CALL(HOOK, NUM))(__VA_ARGS__); \ + } \ +} while (0); -#define call_void_hook(FUNC, ...) \ - do { \ - struct security_hook_list *P; \ - \ - hlist_for_each_entry(P, &security_hook_heads.FUNC, list) \ - P->hook.FUNC(__VA_ARGS__); \ +#define call_void_hook(HOOK, ...) \ + do { \ + LSM_LOOP_UNROLL(__CALL_STATIC_VOID, HOOK, __VA_ARGS__); \ } while (0) -#define call_int_hook(FUNC, ...) ({ \ - int RC = LSM_RET_DEFAULT(FUNC); \ - do { \ - struct security_hook_list *P; \ - \ - hlist_for_each_entry(P, &security_hook_heads.FUNC, list) { \ - RC = P->hook.FUNC(__VA_ARGS__); \ - if (RC != LSM_RET_DEFAULT(FUNC)) \ - break; \ - } \ - } while (0); \ - RC; \ + +#define __CALL_STATIC_INT(NUM, R, HOOK, LABEL, ...) \ +do { \ + if (static_branch_unlikely(&SECURITY_HOOK_ACTIVE_KEY(HOOK, NUM))) { \ + R = static_call(LSM_STATIC_CALL(HOOK, NUM))(__VA_ARGS__); \ + if (R != LSM_RET_DEFAULT(HOOK)) \ + goto LABEL; \ + } \ +} while (0); + +#define call_int_hook(HOOK, ...) \ +({ \ + __label__ out; \ + int RC = LSM_RET_DEFAULT(HOOK); \ + \ + LSM_LOOP_UNROLL(__CALL_STATIC_INT, RC, HOOK, out, __VA_ARGS__); \ +out: \ + RC; \ }) +#define lsm_for_each_hook(scall, NAME) \ + for (scall = static_calls_table.NAME; \ + scall - static_calls_table.NAME < MAX_LSM_COUNT; scall++) \ + if (static_key_enabled(&scall->active->key)) + /* Security operations */ /** @@ -1113,7 +1187,7 @@ int security_settime64(const struct timespec64 *ts, const struct timezone *tz) */ int security_vm_enough_memory_mm(struct mm_struct *mm, long pages) { - struct security_hook_list *hp; + struct lsm_static_call *scall; int cap_sys_admin = 1; int rc; @@ -1124,8 +1198,8 @@ int security_vm_enough_memory_mm(struct mm_struct *mm, long pages) * agree that it should be set it will. If any module * thinks it should not be set it won't. */ - hlist_for_each_entry(hp, &security_hook_heads.vm_enough_memory, list) { - rc = hp->hook.vm_enough_memory(mm, pages); + lsm_for_each_hook(scall, vm_enough_memory) { + rc = scall->hl->hook.vm_enough_memory(mm, pages); if (rc <= 0) { cap_sys_admin = 0; break; @@ -1272,13 +1346,12 @@ int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc) int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param) { - struct security_hook_list *hp; + struct lsm_static_call *scall; int trc; int rc = -ENOPARAM; - hlist_for_each_entry(hp, &security_hook_heads.fs_context_parse_param, - list) { - trc = hp->hook.fs_context_parse_param(fc, param); + lsm_for_each_hook(scall, fs_context_parse_param) { + trc = scall->hl->hook.fs_context_parse_param(fc, param); if (trc == 0) rc = 0; else if (trc != -ENOPARAM) @@ -1508,12 +1581,11 @@ int security_sb_set_mnt_opts(struct super_block *sb, unsigned long kern_flags, unsigned long *set_kern_flags) { - struct security_hook_list *hp; + struct lsm_static_call *scall; int rc = mnt_opts ? -EOPNOTSUPP : LSM_RET_DEFAULT(sb_set_mnt_opts); - hlist_for_each_entry(hp, &security_hook_heads.sb_set_mnt_opts, - list) { - rc = hp->hook.sb_set_mnt_opts(sb, mnt_opts, kern_flags, + lsm_for_each_hook(scall, sb_set_mnt_opts) { + rc = scall->hl->hook.sb_set_mnt_opts(sb, mnt_opts, kern_flags, set_kern_flags); if (rc != LSM_RET_DEFAULT(sb_set_mnt_opts)) break; @@ -1708,7 +1780,7 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, const struct qstr *qstr, const initxattrs initxattrs, void *fs_data) { - struct security_hook_list *hp; + struct lsm_static_call *scall; struct xattr *new_xattrs = NULL; int ret = -EOPNOTSUPP, xattr_count = 0; @@ -1726,9 +1798,8 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, return -ENOMEM; } - hlist_for_each_entry(hp, &security_hook_heads.inode_init_security, - list) { - ret = hp->hook.inode_init_security(inode, dir, qstr, new_xattrs, + lsm_for_each_hook(scall, inode_init_security) { + ret = scall->hl->hook.inode_init_security(inode, dir, qstr, new_xattrs, &xattr_count); if (ret && ret != -EOPNOTSUPP) goto out; @@ -3560,10 +3631,10 @@ int security_task_prctl(int option, unsigned long arg2, unsigned long arg3, { int thisrc; int rc = LSM_RET_DEFAULT(task_prctl); - struct security_hook_list *hp; + struct lsm_static_call *scall; - hlist_for_each_entry(hp, &security_hook_heads.task_prctl, list) { - thisrc = hp->hook.task_prctl(option, arg2, arg3, arg4, arg5); + lsm_for_each_hook(scall, task_prctl) { + thisrc = scall->hl->hook.task_prctl(option, arg2, arg3, arg4, arg5); if (thisrc != LSM_RET_DEFAULT(task_prctl)) { rc = thisrc; if (thisrc != 0) @@ -3969,7 +4040,7 @@ EXPORT_SYMBOL(security_d_instantiate); int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, u32 __user *size, u32 flags) { - struct security_hook_list *hp; + struct lsm_static_call *scall; struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, }; u8 __user *base = (u8 __user *)uctx; u32 entrysize; @@ -4007,13 +4078,13 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, * In the usual case gather all the data from the LSMs. * In the single case only get the data from the LSM specified. */ - hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) { - if (single && lctx.id != hp->lsmid->id) + lsm_for_each_hook(scall, getselfattr) { + if (single && lctx.id != scall->hl->lsmid->id) continue; entrysize = left; if (base) uctx = (struct lsm_ctx __user *)(base + total); - rc = hp->hook.getselfattr(attr, uctx, &entrysize, flags); + rc = scall->hl->hook.getselfattr(attr, uctx, &entrysize, flags); if (rc == -EOPNOTSUPP) { rc = 0; continue; @@ -4062,7 +4133,7 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, int security_setselfattr(unsigned int attr, struct lsm_ctx __user *uctx, u32 size, u32 flags) { - struct security_hook_list *hp; + struct lsm_static_call *scall; struct lsm_ctx *lctx; int rc = LSM_RET_DEFAULT(setselfattr); u64 required_len; @@ -4085,9 +4156,9 @@ int security_setselfattr(unsigned int attr, struct lsm_ctx __user *uctx, goto free_out; } - hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list) - if ((hp->lsmid->id) == lctx->id) { - rc = hp->hook.setselfattr(attr, lctx, size, flags); + lsm_for_each_hook(scall, setselfattr) + if ((scall->hl->lsmid->id) == lctx->id) { + rc = scall->hl->hook.setselfattr(attr, lctx, size, flags); break; } @@ -4110,12 +4181,12 @@ int security_setselfattr(unsigned int attr, struct lsm_ctx __user *uctx, int security_getprocattr(struct task_struct *p, int lsmid, const char *name, char **value) { - struct security_hook_list *hp; + struct lsm_static_call *scall; - hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) { - if (lsmid != 0 && lsmid != hp->lsmid->id) + lsm_for_each_hook(scall, getprocattr) { + if (lsmid != 0 && lsmid != scall->hl->lsmid->id) continue; - return hp->hook.getprocattr(p, name, value); + return scall->hl->hook.getprocattr(p, name, value); } return LSM_RET_DEFAULT(getprocattr); } @@ -4134,12 +4205,12 @@ int security_getprocattr(struct task_struct *p, int lsmid, const char *name, */ int security_setprocattr(int lsmid, const char *name, void *value, size_t size) { - struct security_hook_list *hp; + struct lsm_static_call *scall; - hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) { - if (lsmid != 0 && lsmid != hp->lsmid->id) + lsm_for_each_hook(scall, setprocattr) { + if (lsmid != 0 && lsmid != scall->hl->lsmid->id) continue; - return hp->hook.setprocattr(name, value, size); + return scall->hl->hook.setprocattr(name, value, size); } return LSM_RET_DEFAULT(setprocattr); } @@ -5257,7 +5328,7 @@ int security_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp, const struct flowi_common *flic) { - struct security_hook_list *hp; + struct lsm_static_call *scall; int rc = LSM_RET_DEFAULT(xfrm_state_pol_flow_match); /* @@ -5269,9 +5340,8 @@ int security_xfrm_state_pol_flow_match(struct xfrm_state *x, * For speed optimization, we explicitly break the loop rather than * using the macro */ - hlist_for_each_entry(hp, &security_hook_heads.xfrm_state_pol_flow_match, - list) { - rc = hp->hook.xfrm_state_pol_flow_match(x, xp, flic); + lsm_for_each_hook(scall, xfrm_state_pol_flow_match) { + rc = scall->hl->hook.xfrm_state_pol_flow_match(x, xp, flic); break; } return rc; From patchwork Sat Jun 29 08:43:30 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: KP Singh X-Patchwork-Id: 13716846 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 90F009445; Sat, 29 Jun 2024 08:43:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650628; cv=none; b=IB+kZJeCNGgPhYCzQ9JfllAKliNv4C1/ZUXpyV19wbPVgtu4OPZbzH4hqeqNffFeQ8SeMKTjScSYddwvXk4qsV72/w2ElydzgkoIrqfXm+R9WsztDkYrnduLfd25fppS1OwI7bOyTJ0JhR6v6ruwEbtM9NhCBvtNDxLV44bH//g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650628; c=relaxed/simple; bh=pwcXDjEq8pvG0SPA04i4k1/2ElHxWg2WtlzmNwQUUsg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SNCiU9XR9KZlGoYAfFPnjqk+7Gc10OR+yRlTplV2zH8odbUEFJd/xTOqJ+SLvLFmlvKSjfKktr0FuCrq4sOy6SIgZGmO83JnWWW2N1eZtrf7VwfCELqcW2zaTuY9ldltZ0t+wfLkb/3KGqokCzRvOUe40eFF2OD9pT4MrDzwM3E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Is5EiPUw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Is5EiPUw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53029C2BBFC; Sat, 29 Jun 2024 08:43:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719650628; bh=pwcXDjEq8pvG0SPA04i4k1/2ElHxWg2WtlzmNwQUUsg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Is5EiPUwM4avUUOXdN9akagXYkRCRfmtfO9extIAx3dm3u8xlhcrtB8Xjju9sNdSg RpGtCsMCfqERaxGn2Nwfec9m0LlfJmbxzDvrPyrFfoUproleFA5thqH9Z+gz8Nf3HI hALygzzggYxR3Z25xaqRkumHgs6ZHAFNVXB+H9/AZgkpcxxAV71W7gHAoD0kOq5w2A zqvroPV40GUV3vNBNpjrzROUBN2OO0FHDZXlWxYlpRL9iO8cYVMleBBhKr2DXEmeyb XRoP8ciXECY6EIQU6tOYZFdKjTqTdqYDBY/x1js1KPVL+XdPpnU4ANU10i3PN9Uicq DQBF9v/csEkJg== From: KP Singh To: linux-security-module@vger.kernel.org, bpf@vger.kernel.org Cc: ast@kernel.org, paul@paul-moore.com, casey@schaufler-ca.com, andrii@kernel.org, keescook@chromium.org, daniel@iogearbox.net, renauld@google.com, revest@chromium.org, song@kernel.org, KP Singh Subject: [PATCH v13 4/5] security: Update non standard hooks to use static calls Date: Sat, 29 Jun 2024 10:43:30 +0200 Message-ID: <20240629084331.3807368-5-kpsingh@kernel.org> X-Mailer: git-send-email 2.45.2.803.g4e1b14247a-goog In-Reply-To: <20240629084331.3807368-1-kpsingh@kernel.org> References: <20240629084331.3807368-1-kpsingh@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 There are some LSM hooks which do not use the common pattern followed by other LSM hooks and thus cannot use call_{int, void}_hook macros and instead use lsm_for_each_hook macro which still results in indirect call. There is one additional generalizable pattern where a hook matching an lsmid is called and the indirect calls for these are addressed with the newly added call_hook_with_lsmid macro which internally uses an implementation similar to call_int_hook but has an additional check that matches the lsmid. For the generic case the lsm_for_each_hook macro is updated to accept logic before and after the invocation of the LSM hook (static call) in the unrolled loop. Reviewed-by: Casey Schaufler Reviewed-by: Kees Cook Signed-off-by: KP Singh --- security/security.c | 248 +++++++++++++++++++++++++------------------- 1 file changed, 144 insertions(+), 104 deletions(-) diff --git a/security/security.c b/security/security.c index e0ec185cf125..4f0f35857217 100644 --- a/security/security.c +++ b/security/security.c @@ -948,10 +948,48 @@ out: \ RC; \ }) -#define lsm_for_each_hook(scall, NAME) \ - for (scall = static_calls_table.NAME; \ - scall - static_calls_table.NAME < MAX_LSM_COUNT; scall++) \ - if (static_key_enabled(&scall->active->key)) +/* + * Can be used in the context passed to lsm_for_each_hook to get the lsmid of the + * current hook + */ +#define current_lsmid() _hook_lsmid + +#define __CALL_HOOK(NUM, HOOK, RC, BLOCK_BEFORE, BLOCK_AFTER, ...) \ +do { \ + int __maybe_unused _hook_lsmid; \ + \ + if (static_branch_unlikely(&SECURITY_HOOK_ACTIVE_KEY(HOOK, NUM))) { \ + _hook_lsmid = static_calls_table.HOOK[NUM].hl->lsmid->id; \ + BLOCK_BEFORE \ + RC = static_call(LSM_STATIC_CALL(HOOK, NUM))(__VA_ARGS__); \ + BLOCK_AFTER \ + } \ +} while (0); + +#define lsm_for_each_hook(HOOK, RC, BLOCK_AFTER, ...) \ + LSM_LOOP_UNROLL(__CALL_HOOK, HOOK, RC, ;, BLOCK_AFTER, __VA_ARGS__) + +#define call_hook_with_lsmid(HOOK, LSMID, ...) \ +({ \ + __label__ out; \ + int RC = LSM_RET_DEFAULT(HOOK); \ + \ + LSM_LOOP_UNROLL(__CALL_HOOK, HOOK, RC, \ + /* BLOCK BEFORE INVOCATION */ \ + { \ + if (current_lsmid() != LSMID) \ + continue; \ + }, \ + /* END BLOCK BEFORE INVOCATION */ \ + /* BLOCK AFTER INVOCATION */ \ + { \ + goto out; \ + }, \ + /* END BLOCK AFTER INVOCATION */ \ + __VA_ARGS__); \ +out: \ + RC; \ +}) /* Security operations */ @@ -1187,7 +1225,6 @@ int security_settime64(const struct timespec64 *ts, const struct timezone *tz) */ int security_vm_enough_memory_mm(struct mm_struct *mm, long pages) { - struct lsm_static_call *scall; int cap_sys_admin = 1; int rc; @@ -1198,13 +1235,20 @@ int security_vm_enough_memory_mm(struct mm_struct *mm, long pages) * agree that it should be set it will. If any module * thinks it should not be set it won't. */ - lsm_for_each_hook(scall, vm_enough_memory) { - rc = scall->hl->hook.vm_enough_memory(mm, pages); - if (rc <= 0) { - cap_sys_admin = 0; - break; - } - } + + lsm_for_each_hook( + vm_enough_memory, rc, + /* BLOCK AFTER INVOCATION */ + { + if (rc <= 0) { + cap_sys_admin = 0; + goto out; + } + }, + /* END BLOCK AFTER INVOCATION */ + mm, pages); + +out: return __vm_enough_memory(mm, pages, cap_sys_admin); } @@ -1346,17 +1390,21 @@ int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc) int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param) { - struct lsm_static_call *scall; - int trc; + int trc = LSM_RET_DEFAULT(fs_context_parse_param); int rc = -ENOPARAM; - lsm_for_each_hook(scall, fs_context_parse_param) { - trc = scall->hl->hook.fs_context_parse_param(fc, param); - if (trc == 0) - rc = 0; - else if (trc != -ENOPARAM) - return trc; - } + lsm_for_each_hook( + fs_context_parse_param, trc, + /* BLOCK AFTER INVOCATION */ + { + if (trc == 0) + rc = 0; + else if (trc != -ENOPARAM) + return trc; + }, + /* END BLOCK AFTER INVOCATION */ + fc, param); + return rc; } @@ -1581,15 +1629,19 @@ int security_sb_set_mnt_opts(struct super_block *sb, unsigned long kern_flags, unsigned long *set_kern_flags) { - struct lsm_static_call *scall; int rc = mnt_opts ? -EOPNOTSUPP : LSM_RET_DEFAULT(sb_set_mnt_opts); - lsm_for_each_hook(scall, sb_set_mnt_opts) { - rc = scall->hl->hook.sb_set_mnt_opts(sb, mnt_opts, kern_flags, - set_kern_flags); - if (rc != LSM_RET_DEFAULT(sb_set_mnt_opts)) - break; - } + lsm_for_each_hook( + sb_set_mnt_opts, rc, + /* BLOCK AFTER INVOCATION */ + { + if (rc != LSM_RET_DEFAULT(sb_set_mnt_opts)) + goto out; + }, + /* END BLOCK AFTER INVOCATION */ + sb, mnt_opts, kern_flags, set_kern_flags); + +out: return rc; } EXPORT_SYMBOL(security_sb_set_mnt_opts); @@ -1780,7 +1832,6 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, const struct qstr *qstr, const initxattrs initxattrs, void *fs_data) { - struct lsm_static_call *scall; struct xattr *new_xattrs = NULL; int ret = -EOPNOTSUPP, xattr_count = 0; @@ -1798,18 +1849,21 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, return -ENOMEM; } - lsm_for_each_hook(scall, inode_init_security) { - ret = scall->hl->hook.inode_init_security(inode, dir, qstr, new_xattrs, - &xattr_count); - if (ret && ret != -EOPNOTSUPP) - goto out; + lsm_for_each_hook( + inode_init_security, ret, + /* BLOCK AFTER INVOCATION */ + { /* * As documented in lsm_hooks.h, -EOPNOTSUPP in this context * means that the LSM is not willing to provide an xattr, not * that it wants to signal an error. Thus, continue to invoke * the remaining LSMs. */ - } + if (ret && ret != -EOPNOTSUPP) + goto out; + }, + /* END BLOCK AFTER INVOCATION */ + inode, dir, qstr, new_xattrs, &xattr_count); /* If initxattrs() is NULL, xattr_count is zero, skip the call. */ if (!xattr_count) @@ -3631,16 +3685,21 @@ int security_task_prctl(int option, unsigned long arg2, unsigned long arg3, { int thisrc; int rc = LSM_RET_DEFAULT(task_prctl); - struct lsm_static_call *scall; - - lsm_for_each_hook(scall, task_prctl) { - thisrc = scall->hl->hook.task_prctl(option, arg2, arg3, arg4, arg5); - if (thisrc != LSM_RET_DEFAULT(task_prctl)) { - rc = thisrc; - if (thisrc != 0) - break; - } - } + + lsm_for_each_hook( + task_prctl, thisrc, + /* BLOCK AFTER INVOCATION */ + { + if (thisrc != LSM_RET_DEFAULT(task_prctl)) { + rc = thisrc; + if (thisrc != 0) + goto out; + } + }, + /* END BLOCK AFTER INVOCATION */ + option, arg2, arg3, arg4, arg5); + +out: return rc; } @@ -4040,7 +4099,6 @@ EXPORT_SYMBOL(security_d_instantiate); int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, u32 __user *size, u32 flags) { - struct lsm_static_call *scall; struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, }; u8 __user *base = (u8 __user *)uctx; u32 entrysize; @@ -4078,31 +4136,42 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, * In the usual case gather all the data from the LSMs. * In the single case only get the data from the LSM specified. */ - lsm_for_each_hook(scall, getselfattr) { - if (single && lctx.id != scall->hl->lsmid->id) - continue; - entrysize = left; - if (base) - uctx = (struct lsm_ctx __user *)(base + total); - rc = scall->hl->hook.getselfattr(attr, uctx, &entrysize, flags); - if (rc == -EOPNOTSUPP) { - rc = 0; - continue; - } - if (rc == -E2BIG) { - rc = 0; - left = 0; - toobig = true; - } else if (rc < 0) - return rc; - else - left -= entrysize; + LSM_LOOP_UNROLL( + __CALL_HOOK, getselfattr, rc, + /* BLOCK BEFORE INVOCATION */ + { + if (single && lctx.id != current_lsmid()) + continue; + entrysize = left; + if (base) + uctx = (struct lsm_ctx __user *)(base + total); + }, + /* END BLOCK BEFORE INVOCATION */ + /* BLOCK AFTER INVOCATION */ + { + if (rc == -EOPNOTSUPP) { + rc = 0; + } else { + if (rc == -E2BIG) { + rc = 0; + left = 0; + toobig = true; + } else if (rc < 0) + return rc; + else + left -= entrysize; + + total += entrysize; + count += rc; + if (single) + goto out; + } + }, + /* END BLOCK AFTER INVOCATION */ + attr, uctx, &entrysize, flags); + +out: - total += entrysize; - count += rc; - if (single) - break; - } if (put_user(total, size)) return -EFAULT; if (toobig) @@ -4133,9 +4202,8 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, int security_setselfattr(unsigned int attr, struct lsm_ctx __user *uctx, u32 size, u32 flags) { - struct lsm_static_call *scall; struct lsm_ctx *lctx; - int rc = LSM_RET_DEFAULT(setselfattr); + int rc; u64 required_len; if (flags) @@ -4156,11 +4224,7 @@ int security_setselfattr(unsigned int attr, struct lsm_ctx __user *uctx, goto free_out; } - lsm_for_each_hook(scall, setselfattr) - if ((scall->hl->lsmid->id) == lctx->id) { - rc = scall->hl->hook.setselfattr(attr, lctx, size, flags); - break; - } + rc = call_hook_with_lsmid(setselfattr, lctx->id, attr, lctx, size, flags); free_out: kfree(lctx); @@ -4181,14 +4245,7 @@ int security_setselfattr(unsigned int attr, struct lsm_ctx __user *uctx, int security_getprocattr(struct task_struct *p, int lsmid, const char *name, char **value) { - struct lsm_static_call *scall; - - lsm_for_each_hook(scall, getprocattr) { - if (lsmid != 0 && lsmid != scall->hl->lsmid->id) - continue; - return scall->hl->hook.getprocattr(p, name, value); - } - return LSM_RET_DEFAULT(getprocattr); + return call_hook_with_lsmid(getprocattr, lsmid, p, name, value); } /** @@ -4205,14 +4262,7 @@ int security_getprocattr(struct task_struct *p, int lsmid, const char *name, */ int security_setprocattr(int lsmid, const char *name, void *value, size_t size) { - struct lsm_static_call *scall; - - lsm_for_each_hook(scall, setprocattr) { - if (lsmid != 0 && lsmid != scall->hl->lsmid->id) - continue; - return scall->hl->hook.setprocattr(name, value, size); - } - return LSM_RET_DEFAULT(setprocattr); + return call_hook_with_lsmid(setprocattr, lsmid, name, value, size); } /** @@ -5328,23 +5378,13 @@ int security_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp, const struct flowi_common *flic) { - struct lsm_static_call *scall; - int rc = LSM_RET_DEFAULT(xfrm_state_pol_flow_match); - /* * Since this function is expected to return 0 or 1, the judgment * becomes difficult if multiple LSMs supply this call. Fortunately, * we can use the first LSM's judgment because currently only SELinux * supplies this call. - * - * For speed optimization, we explicitly break the loop rather than - * using the macro */ - lsm_for_each_hook(scall, xfrm_state_pol_flow_match) { - rc = scall->hl->hook.xfrm_state_pol_flow_match(x, xp, flic); - break; - } - return rc; + return call_int_hook(xfrm_state_pol_flow_match, x, xp, flic); } /** From patchwork Sat Jun 29 08:43:31 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: KP Singh X-Patchwork-Id: 13716847 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 207FB3A1B0; Sat, 29 Jun 2024 08:43:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650631; cv=none; b=o+wyvFCaL6p5HjwH6J7XxnWSMksMofnFtw6Q/OPdRu3VxWCYDLdTJ6q1aGIAesCh89MW0U3EEjoaGzYLGRdmdt6qcD5gLk2KrksejF/DFymSikeMcy4B1wo5s0ujs5xSyYcDPWpoAg3uYJ/hTg1SN0EaL9dYGUfBQ30LKs77NLo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719650631; c=relaxed/simple; bh=Crgk1qXG9zWmEXg9/eV4RcF36q1Mme5e5rBDZThYdhw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Tsfn23W03+tip2xq1pdA1hs/aNxAKQflPkpktgnKmRREHP/7/hK6/OciyjHIdpLfzRIG2k7YBcx2KZTgxmSUJ/AMz2DxK0NcEm2zUPQT2S8BJS5bdYBv+040mXJ61mkhYrwEBSiT9oG+pt9TKotMXRwvFrQxHBVY8gZ+xWcENkM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VuwFdOiN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VuwFdOiN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D22E1C4AF0C; Sat, 29 Jun 2024 08:43:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719650631; bh=Crgk1qXG9zWmEXg9/eV4RcF36q1Mme5e5rBDZThYdhw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VuwFdOiN/o5oP30V57+VJR/Ni3j4V54EXkrslFovkHlWw7+D+6Sl+gDYl+juDjilK dS4xcrEw6MTq+omavlnBzSuRcqvUHNkFClGzTWJyLTS39RvlS9X/JmzUqUd0qftGqD dSCRfxMsV17Y32B5jM2PIx6S9sLLhQBpKHJradXU8AoJpoUKyoRb4KEEbZFWQLTbOL GtrZQO/lRdw+ja4N09fawruYeg+LQtxe0xVPA+gwgqusGugCEhTqNVl6KSxErXX/OM rzh272VcKY9A0HzEB5P4wNoSeGzOBX8ZAR9Akqt1YlgzSKtoN8nC3etNus8DXeF5zK 8Oa7h9EE4PrOw== From: KP Singh To: linux-security-module@vger.kernel.org, bpf@vger.kernel.org Cc: ast@kernel.org, paul@paul-moore.com, casey@schaufler-ca.com, andrii@kernel.org, keescook@chromium.org, daniel@iogearbox.net, renauld@google.com, revest@chromium.org, song@kernel.org, KP Singh Subject: [PATCH v13 5/5] bpf: Only enable BPF LSM hooks when an LSM program is attached Date: Sat, 29 Jun 2024 10:43:31 +0200 Message-ID: <20240629084331.3807368-6-kpsingh@kernel.org> X-Mailer: git-send-email 2.45.2.803.g4e1b14247a-goog In-Reply-To: <20240629084331.3807368-1-kpsingh@kernel.org> References: <20240629084331.3807368-1-kpsingh@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net BPF LSM hooks have side-effects (even when a default value's returned) as some hooks end up behaving differently due to the very presence of the hook. The static keys guarding the BPF LSM hooks are disabled by default and enabled only when a BPF program is attached implementing the hook logic. This avoids the issue of the side-effects and also the minor overhead associated with the empty callback. security_file_ioctl: 0xff...0e30 <+0>: endbr64 0xff...0e34 <+4>: nopl 0x0(%rax,%rax,1) 0xff...0e39 <+9>: push %rbp 0xff...0e3a <+10>: push %r14 0xff...0e3c <+12>: push %rbx 0xff...0e3d <+13>: mov %rdx,%rbx 0xff...0e40 <+16>: mov %esi,%ebp 0xff...0e42 <+18>: mov %rdi,%r14 0xff...0e45 <+21>: jmp 0xff...0e57 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Static key enabled for SELinux 0xff...0e47 <+23>: xchg %ax,%ax ^^^^^^^^^^^^^^ Static key disabled for BPF. This gets patched when a BPF LSM program is attached 0xff...0e49 <+25>: xor %eax,%eax 0xff...0e4b <+27>: xchg %ax,%ax 0xff...0e4d <+29>: pop %rbx 0xff...0e4e <+30>: pop %r14 0xff...0e50 <+32>: pop %rbp 0xff...0e51 <+33>: cs jmp 0xff...0000 <__x86_return_thunk> 0xff...0e57 <+39>: endbr64 0xff...0e5b <+43>: mov %r14,%rdi 0xff...0e5e <+46>: mov %ebp,%esi 0xff...0e60 <+48>: mov %rbx,%rdx 0xff...0e63 <+51>: call 0xff...33c0 0xff...0e68 <+56>: test %eax,%eax 0xff...0e6a <+58>: jne 0xff...0e4d 0xff...0e6c <+60>: jmp 0xff...0e47 0xff...0e6e <+62>: endbr64 0xff...0e72 <+66>: mov %r14,%rdi 0xff...0e75 <+69>: mov %ebp,%esi 0xff...0e77 <+71>: mov %rbx,%rdx 0xff...0e7a <+74>: call 0xff...e3b0 0xff...0e7f <+79>: test %eax,%eax 0xff...0e81 <+81>: jne 0xff...0e4d 0xff...0e83 <+83>: jmp 0xff...0e49 0xff...0e85 <+85>: endbr64 0xff...0e89 <+89>: mov %r14,%rdi 0xff...0e8c <+92>: mov %ebp,%esi 0xff...0e8e <+94>: mov %rbx,%rdx 0xff...0e91 <+97>: pop %rbx 0xff...0e92 <+98>: pop %r14 0xff...0e94 <+100>: pop %rbp 0xff...0e95 <+101>: ret This patch enables this by providing a LSM_HOOK_INIT_RUNTIME variant that allows the LSMs to opt-in to hooks which can be toggled at runtime which with security_toogle_hook. Reviewed-by: Kees Cook Acked-by: Casey Schaufler Signed-off-by: KP Singh --- include/linux/lsm_hooks.h | 30 ++++++++++++++++++++++++++++- kernel/bpf/trampoline.c | 40 +++++++++++++++++++++++++++++++++++---- security/bpf/hooks.c | 2 +- security/security.c | 36 ++++++++++++++++++++++++++++++++++- 4 files changed, 101 insertions(+), 7 deletions(-) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index a66ca68485a2..dbe0f40f7f67 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -110,11 +110,14 @@ struct lsm_id { * @scalls: The beginning of the array of static calls assigned to this hook. * @hook: The callback for the hook. * @lsm: The name of the lsm that owns this hook. + * @default_state: The state of the LSM hook when initialized. If set to false, + * the static key guarding the hook will be set to disabled. */ struct security_hook_list { struct lsm_static_call *scalls; union security_list_options hook; const struct lsm_id *lsmid; + bool runtime; } __randomize_layout; /* @@ -165,7 +168,19 @@ static inline struct xattr *lsm_get_xattr_slot(struct xattr *xattrs, #define LSM_HOOK_INIT(NAME, HOOK) \ { \ .scalls = static_calls_table.NAME, \ - .hook = { .NAME = HOOK } \ + .hook = { .NAME = HOOK }, \ + .runtime = false \ + } + +/* + * Initialize hooks that are inactive by default and + * enabled at runtime with security_toggle_hook. + */ +#define LSM_HOOK_INIT_RUNTIME(NAME, HOOK) \ + { \ + .scalls = static_calls_table.NAME, \ + .hook = { .NAME = HOOK }, \ + .runtime = true \ } extern char *lsm_names; @@ -207,4 +222,17 @@ extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[]; extern int lsm_inode_alloc(struct inode *inode); extern struct lsm_static_calls_table static_calls_table __ro_after_init; +#ifdef CONFIG_SECURITY + +int security_toggle_hook(void *addr, bool value); + +#else + +static inline int security_toggle_hook(void *addr, bool value) +{ + return -EINVAL; +} + +#endif /* CONFIG_SECURITY */ + #endif /* ! __LINUX_LSM_HOOKS_H */ diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index f8302a5ca400..69d3eb490a1b 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -523,6 +523,21 @@ static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog) } } +static int bpf_trampoline_toggle_lsm(struct bpf_trampoline *tr, + enum bpf_tramp_prog_type kind) +{ + struct bpf_tramp_link *link; + bool found = false; + + hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) { + if (link->link.prog->type == BPF_PROG_TYPE_LSM) { + found = true; + break; + } + } + return security_toggle_hook(tr->func.addr, found); +} + static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr) { enum bpf_tramp_prog_type kind; @@ -562,11 +577,22 @@ static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_tr hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]); tr->progs_cnt[kind]++; - err = bpf_trampoline_update(tr, true /* lock_direct_mutex */); - if (err) { - hlist_del_init(&link->tramp_hlist); - tr->progs_cnt[kind]--; + + if (link->link.prog->type == BPF_PROG_TYPE_LSM) { + err = bpf_trampoline_toggle_lsm(tr, kind); + if (err) + goto cleanup; } + + err = bpf_trampoline_update(tr, true /* lock_direct_mutex */); + if (err) + goto cleanup; + + return 0; + +cleanup: + hlist_del_init(&link->tramp_hlist); + tr->progs_cnt[kind]--; return err; } @@ -595,6 +621,12 @@ static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_ } hlist_del_init(&link->tramp_hlist); tr->progs_cnt[kind]--; + + if (link->link.prog->type == BPF_PROG_TYPE_LSM) { + err = bpf_trampoline_toggle_lsm(tr, kind); + WARN(err, "BUG: unable to toggle BPF LSM hook"); + } + return bpf_trampoline_update(tr, true /* lock_direct_mutex */); } diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c index 57b9ffd53c98..8452e0835f56 100644 --- a/security/bpf/hooks.c +++ b/security/bpf/hooks.c @@ -9,7 +9,7 @@ static struct security_hook_list bpf_lsm_hooks[] __ro_after_init = { #define LSM_HOOK(RET, DEFAULT, NAME, ...) \ - LSM_HOOK_INIT(NAME, bpf_lsm_##NAME), + LSM_HOOK_INIT_RUNTIME(NAME, bpf_lsm_##NAME), #include #undef LSM_HOOK LSM_HOOK_INIT(inode_free_security, bpf_inode_storage_free), diff --git a/security/security.c b/security/security.c index 4f0f35857217..1c448fe529f9 100644 --- a/security/security.c +++ b/security/security.c @@ -409,7 +409,9 @@ static void __init lsm_static_call_init(struct security_hook_list *hl) __static_call_update(scall->key, scall->trampoline, hl->hook.lsm_func_addr); scall->hl = hl; - static_branch_enable(scall->active); + /* Runtime hooks are inactive by default */ + if (!hl->runtime) + static_branch_enable(scall->active); return; } scall++; @@ -888,6 +890,38 @@ int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, u32 *uctx_len, return rc; } +/** + * security_toggle_hook - Toggle the state of the LSM hook. + * @hook_addr: The address of the hook to be toggled. + * @state: Whether to enable for disable the hook. + * + * Returns 0 on success, -EINVAL if the address is not found. + */ +int security_toggle_hook(void *hook_addr, bool state) +{ + unsigned long num_entries = + (sizeof(static_calls_table) / sizeof(struct lsm_static_call)); + void *scalls_table = ((void *)&static_calls_table); + struct lsm_static_call *scall; + int i; + + for (i = 0; i < num_entries; i++) { + scall = scalls_table + (i * sizeof(struct lsm_static_call)); + if (!scall->hl || !scall->hl->runtime) + continue; + + if (scall->hl->hook.lsm_func_addr != hook_addr) + continue; + + if (state) + static_branch_enable(scall->active); + else + static_branch_disable(scall->active); + return 0; + } + return -EINVAL; +} + /* * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and * can be accessed with: