[moderation] [fs?] KCSAN: data-race in inode_update_timestamps / inode_update_timestamps (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: de0674d9bc69 Merge tag 'for-6.19-rc8-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1786d252580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8e27f4588a0f2183
dashboard link: https://syzkaller.appspot.com/bug?extid=fb252cb04a0a50eb5e20
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/bfedab2f6279/disk-de0674d9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f012a4cb8d82/vmlinux-de0674d9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/acb727c49110/bzImage-de0674d9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fb252c...@syzkaller.appspotmail.com

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

write to 0xffff88810538a9a4 of 4 bytes by task 11596 on cpu 1:
inode_set_mtime_to_ts include/linux/fs.h:1658 [inline]
inode_update_timestamps+0x147/0x270 fs/inode.c:2116
generic_update_time fs/inode.c:2151 [inline]
inode_update_time fs/inode.c:2171 [inline]
file_update_time_flags+0x269/0x300 fs/inode.c:2398
file_update_time+0x17/0x20 fs/inode.c:2419
fault_dirty_shared_page+0xd9/0x390 mm/memory.c:3573
do_shared_fault mm/memory.c:5850 [inline]
do_fault mm/memory.c:5896 [inline]
do_pte_missing mm/memory.c:4404 [inline]
handle_pte_fault mm/memory.c:6276 [inline]
__handle_mm_fault mm/memory.c:6414 [inline]
handle_mm_fault+0x1997/0x3030 mm/memory.c:6583
do_user_addr_fault+0x62f/0x1050 arch/x86/mm/fault.c:1334
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 0xffff88810538a9a4 of 4 bytes by task 11597 on cpu 0:
inode_get_mtime_nsec include/linux/fs.h:1644 [inline]
inode_get_mtime include/linux/fs.h:1650 [inline]
inode_update_timestamps+0x74/0x270 fs/inode.c:2110
generic_update_time fs/inode.c:2151 [inline]
inode_update_time fs/inode.c:2171 [inline]
file_update_time_flags+0x269/0x300 fs/inode.c:2398
file_update_time+0x17/0x20 fs/inode.c:2419
fault_dirty_shared_page+0xd9/0x390 mm/memory.c:3573
do_shared_fault mm/memory.c:5850 [inline]
do_fault mm/memory.c:5896 [inline]
do_pte_missing mm/memory.c:4404 [inline]
handle_pte_fault mm/memory.c:6276 [inline]
__handle_mm_fault mm/memory.c:6414 [inline]
handle_mm_fault+0x1997/0x3030 mm/memory.c:6583
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
rep_movs_alternative+0x4a/0x90 arch/x86/lib/copy_user_64.S:68
copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline]
copy_to_user_iter lib/iov_iter.c:25 [inline]
iterate_ubuf include/linux/iov_iter.h:30 [inline]
iterate_and_advance2 include/linux/iov_iter.h:302 [inline]
iterate_and_advance include/linux/iov_iter.h:330 [inline]
_copy_to_iter+0x141/0xea0 lib/iov_iter.c:197
copy_to_iter include/linux/uio.h:220 [inline]
get_random_bytes_user+0x138/0x2b0 drivers/char/random.c:473
__do_sys_getrandom drivers/char/random.c:1420 [inline]
__se_sys_getrandom drivers/char/random.c:1394 [inline]
__x64_sys_getrandom+0xcf/0x1a0 drivers/char/random.c:1394
x64_sys_call+0x1beb/0x3000 arch/x86/include/generated/asm/syscalls_64.h:319
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x1fc15f2b -> 0x20f28c2b

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 11597 Comm: syz.9.2881 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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