From patchwork Sat Mar 16 12:23:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xu Kuohai X-Patchwork-Id: 13594425 Received: from dggsgout12.his.huawei.com (unknown [45.249.212.56]) (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 90295171AD; Sat, 16 Mar 2024 12:20:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710591610; cv=none; b=JB+iNwNDdYKsEcy7avdo9y2W1RR3sNqpMzLu5Pm7jKDesvUA5y5AQsbdEFdJK6AQjeJ0vaZhM+zSEaHZk54zTJf6lRnD5FjNTqlorBkmywDxkLdu2S0DCHhhFshD08fpgN/GJRCeOafZI5YlwmILUlqeaiGxPKTtOEYNAOKXelc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710591610; c=relaxed/simple; bh=6XYTXU0hZs4EdZDZYUMqxaUi1+XBZVM7Y2TtZSDAPAc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=rpCDJDXd6hswYQOgPLlLz2kxhDj2DZO4w6gjWA/YcSzG8y5s23ptd4a0CDwnouCF0gMfSvecQ8+JPKqrslSpYasWU4SksKAHiuk/2ROfWnnuSr8bcg2gyg7I4t5xXqxWULbAnzasT3WkpNBrRdMG35Ey9l+tQxwRuWfr9zry8zY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.235]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4TxgDG3RBTz4f3kpB; Sat, 16 Mar 2024 20:19:58 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 4D1831A0A09; Sat, 16 Mar 2024 20:20:04 +0800 (CST) Received: from k01.huawei.com (unknown [10.67.174.197]) by APP1 (Coremail) with SMTP id cCh0CgCXsQpyjvVls7GEHA--.54843S2; Sat, 16 Mar 2024 20:20:03 +0800 (CST) From: Xu Kuohai To: bpf@vger.kernel.org, linux-security-module@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Florent Revest , Brendan Jackman , Paul Moore , James Morris , "Serge E . Hallyn" , Khadija Kamran , Casey Schaufler , Ondrej Mosnacek , Kees Cook , John Johansen , Lukas Bulwahn , Roberto Sassu , Shung-Hsi Yu Subject: [PATCH bpf-next 0/5] Fix kernel panic caused by bpf lsm return value Date: Sat, 16 Mar 2024 20:23:54 +0800 Message-Id: <20240316122359.1073787-1-xukuohai@huaweicloud.com> X-Mailer: git-send-email 2.30.2 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: cCh0CgCXsQpyjvVls7GEHA--.54843S2 X-Coremail-Antispam: 1UD129KBjvJXoWxCr4kKF48tFWxCF1rAry3CFg_yoWrZF4xpr 43KF18Gr4IqrWUJF1IkF45Jr13JFZrA3WUXryxJr95AF15Ww1DJr18JrWjqr9xJr4UAr17 tFyqqa1rtry8XaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkFb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Cr0_Gr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I 0E14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l42xK82IY c2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s 026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r4a6rW5MIIYrxkI7VAKI48JMIIF 0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0x vE42xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2 jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07UAkuxUUUUU= X-CM-SenderInfo: 50xn30hkdlqx5xdzvxpfor3voofrz/ X-Patchwork-Delegate: bpf@iogearbox.net From: Xu Kuohai A bpf prog returning positive number attached to file_alloc_security hook will make kernel panic. Here is a panic log: [ 441.235774] BUG: kernel NULL pointer dereference, address: 00000000000009 [ 441.236748] #PF: supervisor write access in kernel mode [ 441.237429] #PF: error_code(0x0002) - not-present page [ 441.238119] PGD 800000000b02f067 P4D 800000000b02f067 PUD b031067 PMD 0 [ 441.238990] Oops: 0002 [#1] PREEMPT SMP PTI [ 441.239546] CPU: 0 PID: 347 Comm: loader Not tainted 6.8.0-rc6-gafe0cbf23373 #22 [ 441.240496] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b4 [ 441.241933] RIP: 0010:alloc_file+0x4b/0x190 [ 441.242485] Code: 8b 04 25 c0 3c 1f 00 48 8b b0 30 0c 00 00 e8 9c fe ff ff 48 3d 00 f0 ff fb [ 441.244820] RSP: 0018:ffffc90000c67c40 EFLAGS: 00010203 [ 441.245484] RAX: ffff888006a891a0 RBX: ffffffff8223bd00 RCX: 0000000035b08000 [ 441.246391] RDX: ffff88800b95f7b0 RSI: 00000000001fc110 RDI: f089cd0b8088ffff [ 441.247294] RBP: ffffc90000c67c58 R08: 0000000000000001 R09: 0000000000000001 [ 441.248209] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000001 [ 441.249108] R13: ffffc90000c67c78 R14: ffffffff8223bd00 R15: fffffffffffffff4 [ 441.250007] FS: 00000000005f3300(0000) GS:ffff88803ec00000(0000) knlGS:0000000000000000 [ 441.251053] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 441.251788] CR2: 00000000000001a9 CR3: 000000000bdc4003 CR4: 0000000000170ef0 [ 441.252688] Call Trace: [ 441.253011] [ 441.253296] ? __die+0x24/0x70 [ 441.253702] ? page_fault_oops+0x15b/0x480 [ 441.254236] ? fixup_exception+0x26/0x330 [ 441.254750] ? exc_page_fault+0x6d/0x1c0 [ 441.255257] ? asm_exc_page_fault+0x26/0x30 [ 441.255792] ? alloc_file+0x4b/0x190 [ 441.256257] alloc_file_pseudo+0x9f/0xf0 [ 441.256760] __anon_inode_getfile+0x87/0x190 [ 441.257311] ? lock_release+0x14e/0x3f0 [ 441.257808] bpf_link_prime+0xe8/0x1d0 [ 441.258315] bpf_tracing_prog_attach+0x311/0x570 [ 441.258916] ? __pfx_bpf_lsm_file_alloc_security+0x10/0x10 [ 441.259605] __sys_bpf+0x1bb7/0x2dc0 [ 441.260070] __x64_sys_bpf+0x20/0x30 [ 441.260533] do_syscall_64+0x72/0x140 [ 441.261004] entry_SYSCALL_64_after_hwframe+0x6e/0x76 [ 441.261643] RIP: 0033:0x4b0349 [ 441.262045] Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 88 [ 441.264355] RSP: 002b:00007fff74daee38 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 [ 441.265293] RAX: ffffffffffffffda RBX: 00007fff74daef30 RCX: 00000000004b0349 [ 441.266187] RDX: 0000000000000040 RSI: 00007fff74daee50 RDI: 000000000000001c [ 441.267114] RBP: 000000000000001b R08: 00000000005ef820 R09: 0000000000000000 [ 441.268018] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004 [ 441.268907] R13: 0000000000000004 R14: 00000000005ef018 R15: 00000000004004e8 The reason is that the positive number returned by bpf prog is not a valid errno, and could not be filtered out with IS_ERR which is used by the file system to check errors. As a result, the file system uses this positive number as file pointer, causing panic. To fix this issue, there are two schemes: 1. Modify the calling sites of file_alloc_security to take positive return values as zero. 2. Make the bpf verifier to ensure no unpredicted value is returned by lsm bpf prog. Considering that hook file_alloc_security never returned positive number before bpf lsm was introduced, and other bpf lsm hooks may have the same problem, scheme 2 is more reasonable. So this patch set adds lsm return value check in verifier to fix it. Xu Kuohai (5): bpf, lsm: Annotate lsm hook return integer with new macro LSM_RET_INT bpf, lsm: Add return value range description for lsm hook bpf, lsm: Add function to read lsm hook return value range bpf, lsm: Check bpf lsm hook return values in verifier bpf: Fix compare error in function retval_range_within include/linux/bpf.h | 1 + include/linux/bpf_lsm.h | 8 + include/linux/lsm_hook_defs.h | 433 +++++++++++++++++----------------- include/linux/lsm_hooks.h | 6 - kernel/bpf/bpf_lsm.c | 66 +++++- kernel/bpf/btf.c | 5 +- kernel/bpf/verifier.c | 59 ++++- security/security.c | 1 + 8 files changed, 348 insertions(+), 231 deletions(-)