[moderation] [fs?] KCSAN: data-race in fill_mg_cmtime / inode_update_timestamps

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bcc8eda6d349 Merge tag 'turbostat-2024.11.30' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17f427c0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2ac8da47c412ab39
dashboard link: https://syzkaller.appspot.com/bug?extid=1062939957ce6d478285
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8b4c7cbd0ed1/disk-bcc8eda6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7d947e3b0427/vmlinux-bcc8eda6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6825cc9e18da/bzImage-bcc8eda6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+106293...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fill_mg_cmtime / inode_update_timestamps

write to 0xffff8881180986c4 of 4 bytes by task 8925 on cpu 0:
inode_set_mtime_to_ts include/linux/fs.h:1648 [inline]
inode_update_timestamps+0x139/0x250 fs/inode.c:2070
generic_update_time fs/inode.c:2105 [inline]
inode_update_time fs/inode.c:2125 [inline]
__file_update_time fs/inode.c:2353 [inline]
file_update_time+0x219/0x2b0 fs/inode.c:2383
shmem_file_write_iter+0x99/0xe0 mm/shmem.c:3290
__kernel_write_iter+0x24b/0x4e0 fs/read_write.c:612
dump_emit_page fs/coredump.c:884 [inline]
dump_user_range+0x3ac/0x550 fs/coredump.c:945
elf_core_dump+0x1bdc/0x1ce0 fs/binfmt_elf.c:2129
do_coredump+0x1898/0x1f40 fs/coredump.c:758
get_signal+0xd4f/0x1000 kernel/signal.c:3001
arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
irqentry_exit_to_user_mode+0xa7/0x120 kernel/entry/common.c:231
irqentry_exit+0x12/0x50 kernel/entry/common.c:334
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

read to 0xffff8881180986c4 of 4 bytes by task 3496 on cpu 1:
inode_get_mtime_nsec include/linux/fs.h:1634 [inline]
inode_get_mtime include/linux/fs.h:1640 [inline]
fill_mg_cmtime+0x58/0x280 fs/stat.c:55
generic_fillattr+0x241/0x330 fs/stat.c:99
shmem_getattr+0x17b/0x200 mm/shmem.c:1177
vfs_getattr_nosec fs/stat.c:208 [inline]
vfs_getattr fs/stat.c:246 [inline]
vfs_statx_path+0x171/0x2d0 fs/stat.c:283
vfs_statx+0xe1/0x170 fs/stat.c:347
vfs_fstatat fs/stat.c:366 [inline]
__do_sys_newfstatat fs/stat.c:530 [inline]
__se_sys_newfstatat+0xdc/0x300 fs/stat.c:524
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:524
x64_sys_call+0x236d/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:263
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: 0x391a99b2 -> 0x39b330c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3496 Comm: syz-executor Tainted: G W 6.12.0-syzkaller-12113-gbcc8eda6d349 #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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