[moderation] [ext4?] KCSAN: data-race in file_update_time / inode_set_ctime_current (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bf61759db409 Merge tag 'sched_ext-for-6.16-rc6-fixes' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1481a38c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c8b73fe883c5b6ae
dashboard link: https://syzkaller.appspot.com/bug?extid=3c180cd9ee1d3742d7f8
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
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/1c515efe0325/disk-bf61759d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/56c4e2b45359/vmlinux-bf61759d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ceaa357b8f6a/bzImage-bf61759d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3c180c...@syzkaller.appspotmail.com

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

write to 0xffff888106eef140 of 8 bytes by task 11549 on cpu 0:
inode_set_ctime_current+0x533/0x770 fs/inode.c:2763
inode_update_timestamps+0x84/0x270 fs/inode.c:2018
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
ext4_page_mkwrite+0x18b/0xba0 fs/ext4/inode.c:6577
do_page_mkwrite mm/memory.c:3378 [inline]
wp_page_shared mm/memory.c:3779 [inline]
do_wp_page+0xe5a/0x2400 mm/memory.c:3998
handle_pte_fault mm/memory.c:6085 [inline]
__handle_mm_fault mm/memory.c:6212 [inline]
handle_mm_fault+0x77d/0x2be0 mm/memory.c:6381
do_user_addr_fault+0x636/0x1090 arch/x86/mm/fault.c:1336
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

read to 0xffff888106eef140 of 8 bytes by task 11556 on cpu 1:
inode_get_ctime_sec include/linux/fs.h:1743 [inline]
inode_get_ctime include/linux/fs.h:1753 [inline]
inode_needs_update_time fs/inode.c:2288 [inline]
file_update_time+0xca/0x2b0 fs/inode.c:2331
ext4_page_mkwrite+0x18b/0xba0 fs/ext4/inode.c:6577
do_page_mkwrite mm/memory.c:3378 [inline]
do_shared_fault mm/memory.c:5666 [inline]
do_fault mm/memory.c:5728 [inline]
do_pte_missing mm/memory.c:4251 [inline]
handle_pte_fault mm/memory.c:6069 [inline]
__handle_mm_fault mm/memory.c:6212 [inline]
handle_mm_fault+0x15cb/0x2be0 mm/memory.c:6381
do_user_addr_fault+0x793/0x1090 arch/x86/mm/fault.c:1387
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
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]
_inline_copy_to_user include/linux/uaccess.h:197 [inline]
_copy_to_user+0x7c/0xa0 lib/usercopy.c:26
copy_to_user include/linux/uaccess.h:225 [inline]
rng_dev_read+0x3ef/0x740 drivers/char/hw_random/core.c:258
do_loop_readv_writev fs/read_write.c:847 [inline]
vfs_readv+0x3f8/0x690 fs/read_write.c:1020
do_preadv fs/read_write.c:1132 [inline]
__do_sys_preadv fs/read_write.c:1179 [inline]
__se_sys_preadv fs/read_write.c:1174 [inline]
__x64_sys_preadv+0xfd/0x1c0 fs/read_write.c:1174
x64_sys_call+0x1503/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:296
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: 0x00000000000000b9 -> 0x00000000000000ba

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 11556 Comm: syz.5.2620 Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================
EXT4-fs error (device loop5): ext4_mb_mark_diskspace_used:4113: comm syz.5.2620: Allocating blocks 497-513 which overlap fs metadata


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[syzbot]

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