KCSAN: data-race in dont_mount / step_into

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 64267926e01b Merge tag 'mmc-v5.18-rc4' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13278dfcf00000
kernel config: https://syzkaller.appspot.com/x/.config?x=703b5f8ca5b2017e
dashboard link: https://syzkaller.appspot.com/bug?extid=7ab22e852c066cf2af27
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7ab22e...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in dont_mount / step_into

read-write to 0xffff88811dd3f0c0 of 4 bytes by task 6446 on cpu 0:
dont_mount+0x27/0x40 include/linux/dcache.h:348
vfs_unlink+0x267/0x3d0 fs/namei.c:4150
do_unlinkat+0x258/0x510 fs/namei.c:4216
__do_sys_unlink fs/namei.c:4264 [inline]
__se_sys_unlink fs/namei.c:4262 [inline]
__x64_sys_unlink+0x2c/0x30 fs/namei.c:4262
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88811dd3f0c0 of 4 bytes by task 1440 on cpu 1:
__d_entry_type include/linux/dcache.h:385 [inline]
d_is_symlink include/linux/dcache.h:415 [inline]
step_into+0x12b/0x760 fs/namei.c:1854
walk_component+0x19a/0x280 fs/namei.c:2026
lookup_last fs/namei.c:2475 [inline]
path_lookupat+0x11d/0x2b0 fs/namei.c:2499
filename_lookup+0x130/0x310 fs/namei.c:2528
user_path_at_empty+0x3e/0x110 fs/namei.c:2851
do_readlinkat+0x98/0x210 fs/stat.c:456
__do_sys_readlink fs/stat.c:489 [inline]
__se_sys_readlink fs/stat.c:486 [inline]
__x64_sys_readlink+0x43/0x50 fs/stat.c:486
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00600008 -> 0x00008008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1440 Comm: udevd Not tainted 5.18.0-rc5-syzkaller-00128-g64267926e01b-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 92e5605a199e Merge tag 'linux_kselftest-fixes-6.10-rc5' of..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1283d851980000
kernel config: https://syzkaller.appspot.com/x/.config?x=704451bc2941bcb0
dashboard link: https://syzkaller.appspot.com/bug?extid=7ab22e852c066cf2af27
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1431852e980000
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f9372939a8c4/disk-92e5605a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a0db084d0cae/vmlinux-92e5605a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f39e8696548d/bzImage-92e5605a.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/d9e337d84a71/mount_3.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7ab22e...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in dont_mount / step_into

read-write to 0xffff888109362c00 of 4 bytes by task 3337 on cpu 0:
dont_mount+0x27/0x40 include/linux/dcache.h:363
vfs_unlink+0x298/0x430 fs/namei.c:4345
do_unlinkat+0x236/0x4c0 fs/namei.c:4407
__do_sys_unlink fs/namei.c:4455 [inline]
__se_sys_unlink fs/namei.c:4453 [inline]
__x64_sys_unlink+0x30/0x40 fs/namei.c:4453
x64_sys_call+0x28a3/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:88
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 0xffff888109362c00 of 4 bytes by task 2786 on cpu 1:
__follow_mount_rcu fs/namei.c:1485 [inline]
handle_mounts fs/namei.c:1536 [inline]
step_into+0xe7/0x810 fs/namei.c:1842
walk_component+0x169/0x230 fs/namei.c:2010
lookup_last fs/namei.c:2469 [inline]
path_lookupat+0x10a/0x2b0 fs/namei.c:2493
filename_lookup+0x127/0x300 fs/namei.c:2522
user_path_at_empty+0x42/0x120 fs/namei.c:2929
do_readlinkat+0x92/0x210 fs/stat.c:499
__do_sys_readlink fs/stat.c:532 [inline]
__se_sys_readlink fs/stat.c:529 [inline]
__x64_sys_readlink+0x47/0x60 fs/stat.c:529
x64_sys_call+0x264b/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:90
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: 0x00600008 -> 0x00008008

Reported by Kernel Concurrency Sanitizer on:

CPU: 1 PID: 2786 Comm: udevd Not tainted 6.10.0-rc4-syzkaller-00045-g92e5605a199e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================


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