[moderation] [exfat?] KCSAN: data-race in _copy_to_iter / fat_set_state (12)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a79a588fc176 Merge tag 'pm-6.16-rc5' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1050f3d4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=eea96b85b0259840
dashboard link: https://syzkaller.appspot.com/bug?extid=a42c3a5dc197dc3daa86
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
CC: [hiro...@mail.parknet.co.jp linki...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org sj155...@samsung.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f0ea4205da34/disk-a79a588f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2b62b224950c/vmlinux-a79a588f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9341eddbbcb3/bzImage-a79a588f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a42c3a...@syzkaller.appspotmail.com

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

write to 0xffff888136bc0025 of 1 bytes by task 12181 on cpu 1:
fat_set_state+0x16c/0x1e0 fs/fat/inode.c:-1
fat_fill_super+0x1875/0x1ce0 fs/fat/inode.c:1832
vfat_fill_super+0x24/0x30 fs/fat/namei_vfat.c:1197
get_tree_bdev_flags+0x28e/0x300 fs/super.c:1681
get_tree_bdev+0x1f/0x30 fs/super.c:1704
vfat_get_tree+0x1c/0x30 fs/fat/namei_vfat.c:1202
vfs_get_tree+0x57/0x1d0 fs/super.c:1804
do_new_mount+0x207/0x680 fs/namespace.c:3902
path_mount+0x4a4/0xb20 fs/namespace.c:4226
do_mount fs/namespace.c:4239 [inline]
__do_sys_mount fs/namespace.c:4450 [inline]
__se_sys_mount+0x28f/0x2e0 fs/namespace.c:4427
__x64_sys_mount+0x67/0x80 fs/namespace.c:4427
x64_sys_call+0xd36/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:166
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

read to 0xffff888136bc0000 of 512 bytes by task 3295 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: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+0x12d/0xe30 lib/iov_iter.c:185
copy_page_to_iter+0x18f/0x2d0 lib/iov_iter.c:362
copy_folio_to_iter include/linux/uio.h:204 [inline]
filemap_read+0x407/0xa00 mm/filemap.c:2762
blkdev_read_iter+0x22d/0x2e0 block/fops.c:833
new_sync_read fs/read_write.c:491 [inline]
vfs_read+0x5ca/0x6f0 fs/read_write.c:572
ksys_read+0xda/0x1a0 fs/read_write.c:715
__do_sys_read fs/read_write.c:724 [inline]
__se_sys_read fs/read_write.c:722 [inline]
__x64_sys_read+0x40/0x50 fs/read_write.c:722
x64_sys_call+0x2d77/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:1
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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3295 Comm: udevd Not tainted 6.16.0-rc4-syzkaller-00308-ga79a588fc176 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


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[syzbot]

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