From: Dmitry Vyukov <dvyukov@google.com>
To: syzbot <syzbot+8c446f45cf5815e9110a@syzkaller.appspotmail.com>
Cc: dhowells@redhat.com, jarkko@kernel.org, jmorris@namei.org,
keyrings@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org, paul@paul-moore.com,
serge@hallyn.com, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [lsm?] [keyrings?] KCSAN: data-race in __se_sys_keyctl / key_task_permission (3)
Date: Thu, 4 Jul 2024 16:38:58 +0200 [thread overview]
Message-ID: <CACT4Y+a1QqOO7XbZrTkppopg3hiUdBkpQLwN8+67PmHJcRHJsQ@mail.gmail.com> (raw)
In-Reply-To: <0000000000004d74cd061c6c9e68@google.com>
On Thu, 4 Jul 2024 at 16:18, syzbot
<syzbot+8c446f45cf5815e9110a@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 8a9c6c40432e Merge tag 'io_uring-6.10-20240703' of git://g..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=113817ae980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=5b9537cd00be479e
> dashboard link: https://syzkaller.appspot.com/bug?extid=8c446f45cf5815e9110a
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f01153f3ec8e/disk-8a9c6c40.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/04b88663a824/vmlinux-8a9c6c40.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/63c518cc63c5/bzImage-8a9c6c40.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8c446f45cf5815e9110a@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KCSAN: data-race in __se_sys_keyctl / key_task_permission
>
> write to 0xffff88812277dd70 of 4 bytes by task 19442 on cpu 0:
> keyctl_setperm_key security/keys/keyctl.c:1098 [inline]
> __do_sys_keyctl security/keys/keyctl.c:1926 [inline]
> __se_sys_keyctl+0xab5/0xbb0 security/keys/keyctl.c:1874
> __x64_sys_keyctl+0x67/0x80 security/keys/keyctl.c:1874
> x64_sys_call+0x2bf5/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:251
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> read to 0xffff88812277dd70 of 4 bytes by task 19441 on cpu 1:
> key_task_permission+0x14a/0x2c0 security/keys/permission.c:55
> lookup_user_key+0x9ea/0xdf0 security/keys/process_keys.c:803
> keyctl_setperm_key security/keys/keyctl.c:1083 [inline]
> __do_sys_keyctl security/keys/keyctl.c:1926 [inline]
> __se_sys_keyctl+0x829/0xbb0 security/keys/keyctl.c:1874
> __x64_sys_keyctl+0x67/0x80 security/keys/keyctl.c:1874
> x64_sys_call+0x2bf5/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:251
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> value changed: 0x3d010000 -> 0x00000000
>
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 1 PID: 19441 Comm: syz.1.4799 Tainted: G W 6.10.0-rc6-syzkaller-00067-g8a9c6c40432e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
> ==================================================================
The code in key_task_permission() looks fishy if it can race with
key->perm updates.
There is possibility for TOCTOU and unintentional re-reads of the field.
prev parent reply other threads:[~2024-07-04 14:39 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-04 14:18 [syzbot] [lsm?] [keyrings?] KCSAN: data-race in __se_sys_keyctl / key_task_permission (3) syzbot
2024-07-04 14:38 ` Dmitry Vyukov [this message]
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