[moderation] [exfat?] KCSAN: data-race in _copy_to_iter / fat_set_state (14)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6b4b543fa187 Merge tag 'parisc-for-7.4-rc1' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10b1bcf1580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e8da0c22f867139b
dashboard link: https://syzkaller.appspot.com/bug?extid=3378b1bef4b92747a197
compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
CC: [ex...@lists.linux.dev hiro...@mail.parknet.co.jp linki...@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/0e18b98d7c7b/disk-6b4b543f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/409ff1890477/vmlinux-6b4b543f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/012382667008/bzImage-6b4b543f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3378b1...@syzkaller.appspotmail.com

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

write to 0xffff88811c180041 of 1 bytes by task 8878 on cpu 0:
fat_set_state+0x16c/0x1e0 fs/fat/inode.c:-1
fat_fill_super+0x181f/0x1c60 fs/fat/inode.c:1880
vfat_fill_super+0x24/0x30 fs/fat/namei_vfat.c:1203
get_tree_bdev_flags+0x291/0x300 fs/super.c:1883
get_tree_bdev+0x1f/0x30 fs/super.c:1906
vfat_get_tree+0x1c/0x30 fs/fat/namei_vfat.c:1208
vfs_get_tree+0x57/0x1d0 fs/super.c:1943
fc_mount fs/namespace.c:1282 [inline]
do_new_mount_fc fs/namespace.c:3910 [inline]
do_new_mount+0x288/0x730 fs/namespace.c:3986
path_mount+0x4ad/0xb90 fs/namespace.c:4337
do_mount fs/namespace.c:4350 [inline]
__do_sys_mount fs/namespace.c:4565 [inline]
__se_sys_mount+0x28c/0x2e0 fs/namespace.c:4542
__x64_sys_mount+0x67/0x80 fs/namespace.c:4542
x64_sys_call+0xc3b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811c180000 of 512 bytes by task 3285 on cpu 1:
instrument_copy_to_user include/linux/instrumented.h:130 [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:302 [inline]
iterate_and_advance include/linux/iov_iter.h:330 [inline]
_copy_to_iter+0x130/0xea0 lib/iov_iter.c:197
copy_page_to_iter+0x174/0x210 lib/iov_iter.c:374
copy_folio_to_iter include/linux/uio.h:204 [inline]
filemap_read+0x3f8/0xad0 mm/filemap.c:2893
blkdev_read_iter+0x27f/0x350 block/fops.c:889
new_sync_read fs/read_write.c:493 [inline]
vfs_read+0x699/0x7c0 fs/read_write.c:574
ksys_read+0xdc/0x1a0 fs/read_write.c:716
__do_sys_read fs/read_write.c:725 [inline]
__se_sys_read fs/read_write.c:723 [inline]
__x64_sys_read+0x40/0x50 fs/read_write.c:723
x64_sys_call+0x2135/0x2550 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3285 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
==================================================================


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