[moderation] [fs?] KCSAN: data-race in file_update_time / inode_update_timestamps (4)

Hello,

syzbot found the following issue on:

HEAD commit: e271ed52b344 Merge tag 'pm-6.16-rc1-3' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14b49570580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1ab8aeea25dd0be4
dashboard link: https://syzkaller.appspot.com/bug?extid=4ed3508d88cbcd42faf6
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
CC: [[email protected] [email protected] [email protected] [email protected] [email protected]]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4d5e70d330bd/disk-e271ed52.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/061178ef182c/vmlinux-e271ed52.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1843cd9a5d1a/bzImage-e271ed52.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

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

read to 0xffff88810464bb00 of 8 bytes by task 8052 on cpu 1:
inode_get_mtime_sec include/linux/fs.h:1697 [inline]
inode_get_mtime include/linux/fs.h:1707 [inline]
inode_needs_update_time fs/inode.c:2284 [inline]
file_update_time+0x6a/0x2b0 fs/inode.c:2331
fault_dirty_shared_page+0xd9/0x3c0 mm/memory.c:3420
do_shared_fault mm/memory.c:5702 [inline]
do_fault mm/memory.c:5748 [inline]
do_pte_missing mm/memory.c:4251 [inline]
handle_pte_fault mm/memory.c:6089 [inline]
__handle_mm_fault mm/memory.c:6232 [inline]
handle_mm_fault+0x165d/0x2be0 mm/memory.c:6401
faultin_page mm/gup.c:1186 [inline]
__get_user_pages+0x1036/0x1fb0 mm/gup.c:1488
__get_user_pages_locked mm/gup.c:1754 [inline]
faultin_page_range+0x10f/0x5b0 mm/gup.c:1978
madvise_populate mm/madvise.c:972 [inline]
madvise_do_behavior+0x120/0x1f20 mm/madvise.c:1729
do_madvise+0x103/0x190 mm/madvise.c:1824
__do_sys_madvise mm/madvise.c:1833 [inline]
__se_sys_madvise mm/madvise.c:1831 [inline]
__x64_sys_madvise+0x64/0x80 mm/madvise.c:1831
x64_sys_call+0x2455/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:29
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff88810464bb00 of 8 bytes by task 8053 on cpu 0:
inode_set_mtime_to_ts include/linux/fs.h:1715 [inline]
inode_update_timestamps+0x136/0x270 fs/inode.c:2022
generic_update_time fs/inode.c:2057 [inline]
inode_update_time fs/inode.c:2077 [inline]
__file_update_time fs/inode.c:2305 [inline]
file_update_time+0x20e/0x2b0 fs/inode.c:2335
fault_dirty_shared_page+0xd9/0x3c0 mm/memory.c:3420
do_shared_fault mm/memory.c:5702 [inline]
do_fault mm/memory.c:5748 [inline]
do_pte_missing mm/memory.c:4251 [inline]
handle_pte_fault mm/memory.c:6089 [inline]
__handle_mm_fault mm/memory.c:6232 [inline]
handle_mm_fault+0x165d/0x2be0 mm/memory.c:6401
faultin_page mm/gup.c:1186 [inline]
__get_user_pages+0x1036/0x1fb0 mm/gup.c:1488
__get_user_pages_locked mm/gup.c:1754 [inline]
faultin_page_range+0x10f/0x5b0 mm/gup.c:1978
madvise_populate mm/madvise.c:972 [inline]
madvise_do_behavior+0x120/0x1f20 mm/madvise.c:1729
do_madvise+0x103/0x190 mm/madvise.c:1824
__do_sys_madvise mm/madvise.c:1833 [inline]
__se_sys_madvise mm/madvise.c:1831 [inline]
__x64_sys_madvise+0x64/0x80 mm/madvise.c:1831
x64_sys_call+0x2455/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:29
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000006842a0c2 -> 0x000000006842a0c3

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 8053 Comm: syz.3.1823 Not tainted 6.15.0-syzkaller-12426-ge271ed52b344 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup