KCSAN: data-race in do_semtimedop / sem_lock

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 06a81c1c Merge tag 'arm64-fixes' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1334b934900000
kernel config: https://syzkaller.appspot.com/x/.config?x=66218120f001565d
dashboard link: https://syzkaller.appspot.com/bug?extid=d232fb2ab0bf8dd1338a
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
CC: [ak...@linux-foundation.org her...@redhat.com ioanna-mari...@canonical.com jo...@joelfernandes.org linux-...@vger.kernel.org man...@colorfullife.com]

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+d232fb...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in do_semtimedop / sem_lock

write to 0xffff888094e236c0 of 4 bytes by task 25678 on cpu 1:
complexmode_tryleave ipc/sem.c:374 [inline]
sem_unlock ipc/sem.c:461 [inline]
do_semtimedop+0x1f21/0x1f50 ipc/sem.c:2124
__do_sys_semop ipc/sem.c:2278 [inline]
__se_sys_semop ipc/sem.c:2275 [inline]
__x64_sys_semop+0x3f/0x50 ipc/sem.c:2275
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888094e236c0 of 4 bytes by task 25687 on cpu 0:
sem_lock+0x67/0x210 ipc/sem.c:415
do_semtimedop+0x84e/0x1f50 ipc/sem.c:2083
__do_sys_semop ipc/sem.c:2278 [inline]
__se_sys_semop ipc/sem.c:2275 [inline]
__x64_sys_semop+0x3f/0x50 ipc/sem.c:2275
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: 25687 Comm: syz-executor.1 Not tainted 5.8.0-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: 25687 Comm: syz-executor.1 Not tainted 5.8.0-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+0x10f/0x19d lib/dump_stack.c:118
panic+0x207/0x64a kernel/panic.c:231
kcsan_report+0x684/0x690 kernel/kcsan/report.c:630
kcsan_setup_watchpoint+0x41e/0x4a0 kernel/kcsan/core.c:540
sem_lock+0x67/0x210 ipc/sem.c:415
do_semtimedop+0x84e/0x1f50 ipc/sem.c:2083
__do_sys_semop ipc/sem.c:2278 [inline]
__se_sys_semop ipc/sem.c:2275 [inline]
__x64_sys_semop+0x3f/0x50 ipc/sem.c:2275
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45ce69
Code: 2d b6 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff3dbab2c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000041
RAX: ffffffffffffffda RBX: 0000000000026b40 RCX: 000000000045ce69
RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 000000000118c000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bfcc
R13: 00007ffd14d86dcf R14: 00007ff3dbab39c0 R15: 000000000118bfcc
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.