[moderation] [ext4?] KCSAN: data-race in file_update_time / inode_update_timestamps (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 02ffd6f89c50 Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10b83d62580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=af364d8777377f6b54bd
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [adilger...@dilger.ca linux...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b67184fa0277/disk-02ffd6f8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3518b1a4506f/vmlinux-02ffd6f8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/77e3c761f22c/bzImage-02ffd6f8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+af364d...@syzkaller.appspotmail.com

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

read to 0xffff8881198ae444 of 4 bytes by task 10549 on cpu 1:
inode_get_mtime_nsec include/linux/fs.h:1708 [inline]
inode_get_mtime include/linux/fs.h:1714 [inline]
inode_needs_update_time fs/inode.c:2283 [inline]
file_update_time+0x87/0x2b0 fs/inode.c:2330
ext4_page_mkwrite+0x18c/0xb90 fs/ext4/inode.c:6704
do_page_mkwrite mm/memory.c:3361 [inline]
wp_page_shared mm/memory.c:3762 [inline]
do_wp_page+0xddb/0x24e0 mm/memory.c:3981
handle_pte_fault mm/memory.c:6068 [inline]
__handle_mm_fault mm/memory.c:6195 [inline]
handle_mm_fault+0x77d/0x2c20 mm/memory.c:6364
fixup_user_fault+0x24c/0x560 mm/gup.c:1608
fault_in_user_writeable+0x5d/0xd0 kernel/futex/core.c:790
futex_lock_pi+0x597/0x780 kernel/futex/pi.c:1109
do_futex+0x21f/0x380 kernel/futex/syscalls.c:-1
__do_sys_futex kernel/futex/syscalls.c:179 [inline]
__se_sys_futex+0x2ed/0x360 kernel/futex/syscalls.c:160
__x64_sys_futex+0x78/0x90 kernel/futex/syscalls.c:160
x64_sys_call+0x2e39/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:203
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 0xffff8881198ae444 of 4 bytes by task 10573 on cpu 0:
inode_set_mtime_to_ts include/linux/fs.h:1722 [inline]
inode_update_timestamps+0x147/0x270 fs/inode.c:2021
generic_update_time fs/inode.c:2056 [inline]
inode_update_time fs/inode.c:2076 [inline]
__file_update_time fs/inode.c:2304 [inline]
file_modified_flags+0x2aa/0x350 fs/inode.c:2375
file_modified+0x17/0x20 fs/inode.c:2391
ext4_fallocate+0x18c/0x2f0 fs/ext4/extents.c:4800
vfs_fallocate+0x3b6/0x400 fs/open.c:342
madvise_remove mm/madvise.c:1049 [inline]
madvise_vma_behavior+0x192d/0x1cf0 mm/madvise.c:1346
madvise_walk_vmas mm/madvise.c:1669 [inline]
madvise_do_behavior+0x5b7/0x970 mm/madvise.c:1885
do_madvise+0x10e/0x190 mm/madvise.c:1978
__do_sys_madvise mm/madvise.c:1987 [inline]
__se_sys_madvise mm/madvise.c:1985 [inline]
__x64_sys_madvise+0x64/0x80 mm/madvise.c:1985
x64_sys_call+0x1f1a/0x2ff0 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: 0x148d5e9e -> 0x179256ca

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 10573 Comm: syz.0.2254 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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