KCSAN: data-race in __fsnotify_parent / vfs_unlink (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 509a1542 Merge tag '5.10-rc6-smb3-fixes' of git://git.samb..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=124126e9500000
kernel config: https://syzkaller.appspot.com/x/.config?x=c949fed53798f819
dashboard link: https://syzkaller.appspot.com/bug?extid=6ef76135150a50f5158f
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+6ef761...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __fsnotify_parent / vfs_unlink

read-write to 0xffff88810d037a80 of 4 bytes by task 28609 on cpu 0:
dont_mount include/linux/dcache.h:354 [inline]
vfs_unlink+0x269/0x3b0 fs/namei.c:3835
do_unlinkat+0x28a/0x4d0 fs/namei.c:3897
__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

read to 0xffff88810d037a80 of 4 bytes by task 28599 on cpu 1:
__fsnotify_parent+0x7d/0x430 fs/notify/fsnotify.c:180
fsnotify_parent include/linux/fsnotify.h:68 [inline]
fsnotify_file include/linux/fsnotify.h:90 [inline]
fsnotify_modify include/linux/fsnotify.h:255 [inline]
vfs_write+0x430/0x7c0 fs/read_write.c:609
ksys_write+0xce/0x180 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:667
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: 28599 Comm: syz-executor.1 Not tainted 5.10.0-rc6-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: 28599 Comm: syz-executor.1 Not tainted 5.10.0-rc6-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
__fsnotify_parent+0x7d/0x430 fs/notify/fsnotify.c:180
fsnotify_parent include/linux/fsnotify.h:68 [inline]
fsnotify_file include/linux/fsnotify.h:90 [inline]
fsnotify_modify include/linux/fsnotify.h:255 [inline]
vfs_write+0x430/0x7c0 fs/read_write.c:609
ksys_write+0xce/0x180 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:667
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:00007ff17e7f3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000003ad40 RCX: 000000000045deb9
RDX: 000000000d4ba0ff RSI: 00000000200009c0 RDI: 0000000000000004
RBP: 000000000119bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119bf2c
R13: 00007ffded86078f R14: 00007ff17e7f49c0 R15: 000000000119bf2c
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.