From patchwork Wed Jul 31 12:14:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13748604 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 5E0312E40E; Wed, 31 Jul 2024 12:19:57 +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=1722428398; cv=none; b=V6Q+yyf9NW/r2y9QC/O7Dr+/5G6qt/jVWTSNl1rc40I5+t9MhfLVsDdT8uxYCllkU/P0vxguMHJnKCXq8QpY41GD8bZdgJ+WGuMhIG+yRQfikDa/qtATYWyuI7krSpCroep63FcFm8Qhb5X0A/YMJcG6CfvNFBIXmY27VCtLkbY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722428398; c=relaxed/simple; bh=ePficpvEcImrfJYxAgXbKEtc0fEAKvtwRYbBp5UBY5U=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=psLeIQtS5CE17txm+XOpubE/2dFpMlkM3VXFiuQ3Kl8fS5Mrc+8iIvqLUqfsxRiCDSIxu+VlrngeE8QwJ/I7ok/sFWmy6dGedmrKioyxlAxvOTVDQ+OUSIX9IC+SdCHW29FXvXoHC1t9MtkVvdef4QKIF/CXQtl3RXEG3Q0T01c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=N5z4LPHT; 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="N5z4LPHT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BDE8C4AF10; Wed, 31 Jul 2024 12:19:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722428397; bh=ePficpvEcImrfJYxAgXbKEtc0fEAKvtwRYbBp5UBY5U=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=N5z4LPHTw2OgDbdtQeBybzS6XIwOGL1fjR7KFUik5rxyoEBjxaQ3W3drlCakhlZUU kUlRwucPRuSOirr0e76ZTYIXP5pbKtL4n04J0BrBcMtNHhCRxJHLEBLKHtSBI7jchV aSdf6/dyLyREZfeQrxyL3caZS11DCrzu1GOUFdOluidelvyqy1JIh0LzqkuYUgtvni 3R4rXU1pRokjBLJ0y6zEvXOuCEseqRnzCighZTdsG0fZRNuCsrv9iXY1Ci1RtN/mPn flgV9vKEi4QOf+jtQYlEnqoYd76C9KZRg+FGJdQTxBF2q1Y/h3fPBrFsr0MBi4bZsV P3hhoPeWU+lOw== From: Mark Brown Date: Wed, 31 Jul 2024 13:14:15 +0100 Subject: [PATCH RFT v7 9/9] selftests/clone3: Test shadow stack support Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240731-clone3-shadow-stack-v7-9-a9532eebfb1d@kernel.org> References: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org> In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook X-Mailer: b4 0.15-dev-37811 X-Developer-Signature: v=1; a=openpgp-sha256; l=9005; i=broonie@kernel.org; h=from:subject:message-id; bh=ePficpvEcImrfJYxAgXbKEtc0fEAKvtwRYbBp5UBY5U=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBmqiuyYPhBHao4vXI4T/9r+3pdRhGkDCR1z5IJffA7 XKBMIBCJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZqorsgAKCRAk1otyXVSH0M2bB/ 9qTutRPtqwO+Sjefyr7BuGVaNCBNpazam00SDX9Wa6x44sUVX5MESm/Mqs9iYAKE3u6NJXkod3gsbl vQp/k2ie3jsOa7BMDxbo+gl7RWEZn9GqrfCWtQsKzvh8Rlj5YXpjQWcOKVxYGctLpvYaH/rNEHkBGK TUQ/bWlQkwgt7l9LvVkaU2QOYTKc/h4osnWTHmbI6sd9mgspinThJG7DKYHeguNq+ECbvMJipAt1L9 59Zl62XFqjmEPjsnEDPiXIr7hFH+fWsXPhLR7FKGVmWtZ3UKLQD2UdkMWniYweuwUwlPYMU+K3Rnx9 Sqbu/hHkM+pjZLAtCBJ4XYDRNL68XQ X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Add basic test coverage for specifying the shadow stack for a newly created thread via clone3(), including coverage of the newly extended argument structure. We check that a user specified shadow stack can be provided, and that invalid combinations of parameters are rejected. In order to facilitate testing on systems without userspace shadow stack support we manually enable shadow stacks on startup, this is architecture specific due to the use of an arch_prctl() on x86. Due to interactions with potential userspace locking of features we actually detect support for shadow stacks on the running system by attempting to allocate a shadow stack page during initialisation using map_shadow_stack(), warning if this succeeds when the enable failed. In order to allow testing of user configured shadow stacks on architectures with that feature we need to ensure that we do not return from the function where the clone3() syscall is called in the child process, doing so would trigger a shadow stack underflow. To do this we use inline assembly rather than the standard syscall wrapper to call clone3(). In order to avoid surprises we also use a syscall rather than the libc exit() function., this should be overly cautious. Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 134 +++++++++++++++++++++- tools/testing/selftests/clone3/clone3_selftests.h | 38 ++++++ 2 files changed, 171 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c index 26221661e9ae..81c2e8648e8b 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -3,6 +3,7 @@ /* Based on Christian Brauner's clone3() example */ #define _GNU_SOURCE +#include #include #include #include @@ -11,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -19,8 +21,12 @@ #include #include "../kselftest.h" +#include "../ksft_shstk.h" #include "clone3_selftests.h" +static bool shadow_stack_supported; +static size_t max_supported_args_size; + enum test_mode { CLONE3_ARGS_NO_TEST, CLONE3_ARGS_ALL_0, @@ -28,6 +34,10 @@ enum test_mode { CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG, CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG, CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG, + CLONE3_ARGS_SHADOW_STACK, + CLONE3_ARGS_SHADOW_STACK_NO_SIZE, + CLONE3_ARGS_SHADOW_STACK_NO_POINTER, + CLONE3_ARGS_SHADOW_STACK_NO_TOKEN, }; typedef bool (*filter_function)(void); @@ -44,6 +54,44 @@ struct test { filter_function filter; }; + +/* + * We check for shadow stack support by attempting to use + * map_shadow_stack() since features may have been locked by the + * dynamic linker resulting in spurious errors when we attempt to + * enable on startup. We warn if the enable failed. + */ +static void test_shadow_stack_supported(void) +{ + long ret; + + ret = syscall(__NR_map_shadow_stack, 0, getpagesize(), 0); + if (ret == -1) { + ksft_print_msg("map_shadow_stack() not supported\n"); + } else if ((void *)ret == MAP_FAILED) { + ksft_print_msg("Failed to map shadow stack\n"); + } else { + ksft_print_msg("Shadow stack supportd\n"); + shadow_stack_supported = true; + + if (!shadow_stack_enabled) + ksft_print_msg("Mapped but did not enable shadow stack\n"); + } +} + +static unsigned long long get_shadow_stack_page(unsigned long flags) +{ + unsigned long long page; + + page = syscall(__NR_map_shadow_stack, 0, getpagesize(), flags); + if ((void *)page == MAP_FAILED) { + ksft_print_msg("map_shadow_stack() failed: %d\n", errno); + return 0; + } + + return page; +} + static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) { struct __clone_args args = { @@ -89,6 +137,21 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG: args.exit_signal = 0x00000000000000f0ULL; break; + case CLONE3_ARGS_SHADOW_STACK: + /* We need to specify a normal stack too to avoid corruption */ + args.shadow_stack = get_shadow_stack_page(SHADOW_STACK_SET_TOKEN); + args.shadow_stack_size = getpagesize(); + break; + case CLONE3_ARGS_SHADOW_STACK_NO_POINTER: + args.shadow_stack_size = getpagesize(); + break; + case CLONE3_ARGS_SHADOW_STACK_NO_SIZE: + args.shadow_stack = get_shadow_stack_page(SHADOW_STACK_SET_TOKEN); + break; + case CLONE3_ARGS_SHADOW_STACK_NO_TOKEN: + args.shadow_stack = get_shadow_stack_page(0); + args.shadow_stack_size = getpagesize(); + break; } memcpy(&args_ext.args, &args, sizeof(struct __clone_args)); @@ -102,7 +165,12 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) if (pid == 0) { ksft_print_msg("I am the child, my PID is %d\n", getpid()); - _exit(EXIT_SUCCESS); + /* + * Use a raw syscall to ensure we don't get issues + * with manually specified shadow stack and exit handlers. + */ + syscall(__NR_exit, EXIT_SUCCESS); + ksft_print_msg("CHILD FAILED TO EXIT PID is %d\n", getpid()); } ksft_print_msg("I am the parent (%d). My child's pid is %d\n", @@ -191,6 +259,26 @@ static bool no_timenamespace(void) return true; } +static bool have_shadow_stack(void) +{ + if (shadow_stack_supported) { + ksft_print_msg("Shadow stack supported\n"); + return true; + } + + return false; +} + +static bool no_shadow_stack(void) +{ + if (!shadow_stack_supported) { + ksft_print_msg("Shadow stack not supported\n"); + return true; + } + + return false; +} + static size_t page_size_plus_8(void) { return getpagesize() + 8; @@ -334,6 +422,47 @@ static const struct test tests[] = { .expected = -EINVAL, .test_mode = CLONE3_ARGS_NO_TEST, }, + { + .name = "Shadow stack on system with shadow stack", + .size = 0, + .expected = 0, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack with no pointer", + .size = 0, + .expected = -EINVAL, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_NO_POINTER, + }, + { + .name = "Shadow stack with no size", + .size = 0, + .expected = -EINVAL, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_NO_SIZE, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack with no token", + .flags = CLONE_VM, + .size = 0, + .expected = SIGSEGV, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_NO_TOKEN, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack on system without shadow stack", + .flags = CLONE_VM, + .size = 0, + .expected = -EINVAL, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK, + .filter = have_shadow_stack, + }, }; int main(int argc, char *argv[]) @@ -341,9 +470,12 @@ int main(int argc, char *argv[]) size_t size; int i; + enable_shadow_stack(); + ksft_print_header(); ksft_set_plan(ARRAY_SIZE(tests)); test_clone3_supported(); + test_shadow_stack_supported(); for (i = 0; i < ARRAY_SIZE(tests); i++) test_clone3(&tests[i]); diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h index 39b5dcba663c..38d82934668a 100644 --- a/tools/testing/selftests/clone3/clone3_selftests.h +++ b/tools/testing/selftests/clone3/clone3_selftests.h @@ -31,12 +31,50 @@ struct __clone_args { __aligned_u64 set_tid; __aligned_u64 set_tid_size; __aligned_u64 cgroup; +#ifndef CLONE_ARGS_SIZE_VER2 +#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#endif + __aligned_u64 shadow_stack; + __aligned_u64 shadow_stack_size; +#ifndef CLONE_ARGS_SIZE_VER3 +#define CLONE_ARGS_SIZE_VER3 104 /* sizeof fourth published struct */ +#endif }; +/* + * For architectures with shadow stack support we need to be + * absolutely sure that the clone3() syscall will be inline and not a + * function call so we open code. + */ +#ifdef __x86_64__ +static pid_t __always_inline sys_clone3(struct __clone_args *args, size_t size) +{ + long ret; + register long _num __asm__ ("rax") = __NR_clone3; + register long _args __asm__ ("rdi") = (long)(args); + register long _size __asm__ ("rsi") = (long)(size); + + __asm__ volatile ( + "syscall\n" + : "=a"(ret) + : "r"(_args), "r"(_size), + "0"(_num) + : "rcx", "r11", "memory", "cc" + ); + + if (ret < 0) { + errno = -ret; + return -1; + } + + return ret; +} +#else static pid_t sys_clone3(struct __clone_args *args, size_t size) { return syscall(__NR_clone3, args, size); } +#endif static inline void test_clone3_supported(void) {