Re: [syzbot] [lsm?] [keyrings?] KCSAN: data-race in __se_sys_keyctl / key_task_permission (3)
From: Dmitry Vyukov <dvyukov@google.com>
Date: 2024-07-04 14:39:11
Also in:
keyrings, lkml
On Thu, 4 Jul 2024 at 16:18, syzbot [off-list ref] 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.