KCSAN: data-race in __mark_inode_dirty / iput (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4429f14a Merge tag 'block-5.10-2020-11-07' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b0ee2a500000
kernel config: https://syzkaller.appspot.com/x/.config?x=76dfc991796328d4
dashboard link: https://syzkaller.appspot.com/bug?extid=a6c6ba3248c3621cf7cf
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+a6c6ba...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __mark_inode_dirty / iput

write to 0xffff8881027a4c88 of 8 bytes by task 4893 on cpu 1:
__mark_inode_dirty+0x212/0x740 fs/fs-writeback.c:2290
generic_update_time fs/inode.c:1764 [inline]
update_time fs/inode.c:1777 [inline]
touch_atime+0x157/0x1a0 fs/inode.c:1848
do_readlinkat+0x15d/0x200 fs/stat.c:418
__do_sys_readlink fs/stat.c:440 [inline]
__se_sys_readlink fs/stat.c:437 [inline]
__x64_sys_readlink+0x43/0x50 fs/stat.c:437
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881027a4c88 of 8 bytes by task 27468 on cpu 0:
iput+0x2e/0x510 fs/inode.c:1670
do_unlinkat+0x2c9/0x4d0 fs/namei.c:3903
__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: 0 PID: 27468 Comm: systemd-udevd Not tainted 5.10.0-rc2-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: 0 PID: 27468 Comm: systemd-udevd Not tainted 5.10.0-rc2-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
iput+0x2e/0x510 fs/inode.c:1670
do_unlinkat+0x2c9/0x4d0 fs/namei.c:3903
__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: 0033:0x7f77de0250e7
Code: f0 ff ff 73 01 c3 48 8b 0d ae bd 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 57 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 81 bd 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffd2bd4c578 EFLAGS: 00000293 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 000056529b164d90 RCX: 00007f77de0250e7
RDX: 00007ffd2bd4c594 RSI: 000056529a4707dc RDI: 00007ffd2bd4c580
RBP: 00000000000015dd R08: 0000000000000001 R09: 0000000000000014
R10: 0000000000000064 R11: 0000000000000293 R12: 00007ffd2bd4c690
R13: 000056529b164d90 R14: 0000000000000003 R15: 000000000000000e
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.