[moderation] [ext4?] KCSAN: data-race in _copy_to_iter / string (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bfa8f18691ed Merge tag 'scsi-misc' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17663aa5180000
kernel config: https://syzkaller.appspot.com/x/.config?x=5bd3d8ca9a9838e3
dashboard link: https://syzkaller.appspot.com/bug?extid=681952c87c120dd20b21
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 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/e5b1c905dbbe/disk-bfa8f186.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/59eab6cdf6db/vmlinux-bfa8f186.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a9a927132daf/bzImage-bfa8f186.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+681952...@syzkaller.appspotmail.com

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

write to 0xffff888140f2b050 of 1 bytes by task 4093 on cpu 1:
string_nocheck lib/vsprintf.c:650 [inline]
string+0x16c/0x210 lib/vsprintf.c:728
bdev_name+0x140/0x240 lib/vsprintf.c:968
pointer+0x5e3/0xd20 lib/vsprintf.c:2474
vsnprintf+0x861/0xe30 lib/vsprintf.c:2828
snprintf+0x87/0xb0 lib/vsprintf.c:2959
ext4_multi_mount_protect+0x4d0/0x5e0 fs/ext4/mmp.c:386
__ext4_fill_super fs/ext4/super.c:5358 [inline]
ext4_fill_super+0x292b/0x39d0 fs/ext4/super.c:5699
get_tree_bdev+0x253/0x2e0 fs/super.c:1632
ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5731
vfs_get_tree+0x56/0x1d0 fs/super.c:1797
do_new_mount+0x227/0x690 fs/namespace.c:3352
path_mount+0x49b/0xb30 fs/namespace.c:3679
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount+0x27f/0x2d0 fs/namespace.c:3875
__x64_sys_mount+0x67/0x80 fs/namespace.c:3875
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x6d/0x75

read to 0xffff888140f2b000 of 512 bytes by task 3362 on cpu 0:
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:29 [inline]
iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
iterate_and_advance include/linux/iov_iter.h:271 [inline]
_copy_to_iter+0x126/0xb30 lib/iov_iter.c:185
copy_page_to_iter+0x171/0x2b0 lib/iov_iter.c:362
copy_folio_to_iter include/linux/uio.h:180 [inline]
filemap_read+0x42c/0x690 mm/filemap.c:2652
blkdev_read_iter+0x217/0x2c0 block/fops.c:754
call_read_iter include/linux/fs.h:2102 [inline]
new_sync_read fs/read_write.c:395 [inline]
vfs_read+0x5bc/0x6b0 fs/read_write.c:476
ksys_read+0xeb/0x1b0 fs/read_write.c:619
__do_sys_read fs/read_write.c:629 [inline]
__se_sys_read fs/read_write.c:627 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:627
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x6d/0x75

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3362 Comm: udevd Not tainted 6.8.0-syzkaller-13161-gbfa8f18691ed #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
==================================================================


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