KCSAN: data-race in dput / vfs_rmdir (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: eccc8767 Merge branch 'fixes' of git://git.kernel.org/pub/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12c956aa500000
kernel config: https://syzkaller.appspot.com/x/.config?x=671e27f23e60a67b
dashboard link: https://syzkaller.appspot.com/bug?extid=e8c40c3114482d1255c2
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
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+e8c40c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in dput / vfs_rmdir

read-write to 0xffff88810d975300 of 4 bytes by task 15149 on cpu 0:
dont_mount include/linux/dcache.h:354 [inline]
vfs_rmdir+0x193/0x290 fs/namei.c:3719
do_rmdir+0x16e/0x300 fs/namei.c:3774
__do_sys_rmdir fs/namei.c:3792 [inline]
__se_sys_rmdir fs/namei.c:3790 [inline]
__x64_sys_rmdir+0x2c/0x30 fs/namei.c:3790
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810d975300 of 4 bytes by task 15147 on cpu 1:
fast_dput fs/dcache.c:746 [inline]
dput+0x2f/0x420 fs/dcache.c:865
path_put fs/namei.c:496 [inline]
do_unlinkat+0x37a/0x4d0 fs/namei.c:3912
__do_sys_unlink fs/namei.c:3943 [inline]
__se_sys_unlink fs/namei.c:3941 [inline]
__x64_sys_unlink+0x2c/0x30 fs/namei.c:3941
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15147 Comm: syz-executor.5 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 15147 Comm: syz-executor.5 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x116/0x15d lib/dump_stack.c:118
panic+0x1e7/0x5fa kernel/panic.c:231
kcsan_report+0x67b/0x680 kernel/kcsan/report.c:634
kcsan_setup_watchpoint+0x46a/0x4d0 kernel/kcsan/core.c:568
fast_dput fs/dcache.c:746 [inline]
dput+0x2f/0x420 fs/dcache.c:865
path_put fs/namei.c:496 [inline]
do_unlinkat+0x37a/0x4d0 fs/namei.c:3912
__do_sys_unlink fs/namei.c:3943 [inline]
__se_sys_unlink fs/namei.c:3941 [inline]
__x64_sys_unlink+0x2c/0x30 fs/namei.c:3941
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45deb9
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f1729513c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000038180 RCX: 000000000045deb9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040
RBP: 000000000118bff8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bfd4
R13: 00007fff00ec12ff R14: 00007f17295149c0 R15: 000000000118bfd4
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.