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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d8a9a4b11a13 Merge tag 'v7.0-rc6-smb3-client-fix' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14a48e06580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3a78dd265deac3a9
dashboard link: https://syzkaller.appspot.com/bug?extid=ca31f410b18d1d1ddbbe
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
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/d57ab69594ea/disk-d8a9a4b1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/465f17bdc2a1/vmlinux-d8a9a4b1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c658f4e05ddd/bzImage-d8a9a4b1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ca31f4...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in inode_update_time / inode_update_time

write to 0xffff888100446a14 of 4 bytes by task 6641 on cpu 1:
inode_set_mtime_to_ts include/linux/fs.h:1659 [inline]
inode_update_cmtime fs/inode.c:2139 [inline]
inode_update_time+0x2cc/0x360 fs/inode.c:2164
generic_update_time fs/inode.c:2195 [inline]
file_update_time_flags+0x277/0x2e0 fs/inode.c:2428
file_update_time+0x17/0x20 fs/inode.c:2449
fault_dirty_shared_page+0xd9/0x380 mm/memory.c:3631
do_shared_fault mm/memory.c:5891 [inline]
do_fault mm/memory.c:5937 [inline]
do_pte_missing mm/memory.c:4477 [inline]
handle_pte_fault mm/memory.c:6317 [inline]
__handle_mm_fault mm/memory.c:6455 [inline]
handle_mm_fault+0x19a1/0x3020 mm/memory.c:6624
do_user_addr_fault+0x3fd/0x1050 arch/x86/mm/fault.c:1385
handle_page_fault arch/x86/mm/fault.c:1474 [inline]
exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1527
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

read to 0xffff888100446a14 of 4 bytes by task 6642 on cpu 0:
inode_get_mtime_nsec include/linux/fs.h:1645 [inline]
inode_get_mtime include/linux/fs.h:1651 [inline]
inode_update_cmtime fs/inode.c:2111 [inline]
inode_update_time+0xe3/0x360 fs/inode.c:2164
generic_update_time fs/inode.c:2195 [inline]
file_update_time_flags+0x277/0x2e0 fs/inode.c:2428
file_update_time+0x17/0x20 fs/inode.c:2449
fault_dirty_shared_page+0xd9/0x380 mm/memory.c:3631
do_shared_fault mm/memory.c:5891 [inline]
do_fault mm/memory.c:5937 [inline]
do_pte_missing mm/memory.c:4477 [inline]
handle_pte_fault mm/memory.c:6317 [inline]
__handle_mm_fault mm/memory.c:6455 [inline]
handle_mm_fault+0x19a1/0x3020 mm/memory.c:6624
faultin_page mm/gup.c:1126 [inline]
__get_user_pages+0x1023/0x1ea0 mm/gup.c:1428
__get_user_pages_locked mm/gup.c:1752 [inline]
__gup_longterm_locked+0x4c7/0xe30 mm/gup.c:2481
gup_fast_fallback+0x1f3/0x13c0 mm/gup.c:3209
pin_user_pages_fast+0x5f/0x90 mm/gup.c:3315
io_pin_pages+0xba/0x170 io_uring/memmap.c:63
io_sqe_buffer_register+0x1fd/0x1210 io_uring/rsrc.c:792
io_sqe_buffers_register+0x24e/0x4e0 io_uring/rsrc.c:904
__io_uring_register io_uring/register.c:739 [inline]
__do_sys_io_uring_register io_uring/register.c:1035 [inline]
__se_sys_io_uring_register+0xdd6/0x12d0 io_uring/register.c:1012
__x64_sys_io_uring_register+0x55/0x70 io_uring/register.c:1012
x64_sys_call+0x2be0/0x3020 arch/x86/include/generated/asm/syscalls_64.h:428
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x2ad36db1 -> 0x2eff8b45

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6642 Comm: syz.4.739 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


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