[moderation] [ext4?] KCSAN: data-race in _copy_to_iter / string (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13ded818580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5e179f449c1ff36
dashboard link: https://syzkaller.appspot.com/bug?extid=09bb933e216157f6898f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
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/03424ff7eaf8/disk-ccb98cce.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf709286daff/vmlinux-ccb98cce.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f2eeb3fc93f0/bzImage-ccb98cce.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+09bb93...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in _copy_to_iter / string

write to 0xffff88810b3d1050 of 1 bytes by task 3477 on cpu 0:
string_nocheck lib/vsprintf.c:650 [inline]
string+0x16c/0x210 lib/vsprintf.c:728
bdev_name+0x140/0x250 lib/vsprintf.c:968
pointer+0x5e3/0xd20 lib/vsprintf.c:2498
vsnprintf+0x861/0xe30 lib/vsprintf.c:2852
snprintf+0x87/0xb0 lib/vsprintf.c:2983
ext4_multi_mount_protect+0x4d0/0x5e0 fs/ext4/mmp.c:386
__ext4_fill_super fs/ext4/super.c:5395 [inline]
ext4_fill_super+0x299a/0x3a10 fs/ext4/super.c:5733
get_tree_bdev_flags+0x29f/0x310 fs/super.c:1636
get_tree_bdev+0x1f/0x30 fs/super.c:1659
ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5765
vfs_get_tree+0x56/0x1e0 fs/super.c:1814
do_new_mount+0x227/0x690 fs/namespace.c:3507
path_mount+0x49b/0xb30 fs/namespace.c:3834
do_mount fs/namespace.c:3847 [inline]
__do_sys_mount fs/namespace.c:4057 [inline]
__se_sys_mount+0x27c/0x2d0 fs/namespace.c:4034
__x64_sys_mount+0x67/0x80 fs/namespace.c:4034
x64_sys_call+0x2c84/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810b3d1000 of 512 bytes by task 3286 on cpu 1:
instrument_copy_to_user include/linux/instrumented.h:113 [inline]
copy_to_user_iter lib/iov_iter.c:24 [inline]
iterate_ubuf include/linux/iov_iter.h:30 [inline]
iterate_and_advance2 include/linux/iov_iter.h:300 [inline]
iterate_and_advance include/linux/iov_iter.h:328 [inline]
_copy_to_iter+0x130/0xd00 lib/iov_iter.c:185
copy_page_to_iter+0x171/0x2b0 lib/iov_iter.c:362
copy_folio_to_iter include/linux/uio.h:189 [inline]
filemap_read+0x42d/0x6a0 mm/filemap.c:2697
blkdev_read_iter+0x20e/0x2c0 block/fops.c:770
new_sync_read fs/read_write.c:484 [inline]
vfs_read+0x5dc/0x700 fs/read_write.c:565
ksys_read+0xe8/0x1b0 fs/read_write.c:708
__do_sys_read fs/read_write.c:717 [inline]
__se_sys_read fs/read_write.c:715 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:715
x64_sys_call+0x2874/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3286 Comm: udevd Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


---
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 syzk...@googlegroups.com.

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

[syzbot]

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