[moderation] [exfat?] KCSAN: data-race in _copy_to_iter / fat_set_state (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c3f38fa61af7 Linux 6.10-rc2
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f9a6ba980000
kernel config: https://syzkaller.appspot.com/x/.config?x=8c00b51a1d411353
dashboard link: https://syzkaller.appspot.com/bug?extid=b8bb893c38717b2819d8
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
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/eef327542baf/disk-c3f38fa6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8e83b758a6a4/vmlinux-c3f38fa6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/132dca419132/bzImage-c3f38fa6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b8bb89...@syzkaller.appspotmail.com

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

write to 0xffff88810e251025 of 1 bytes by task 3705 on cpu 0:
fat_set_state+0x16e/0x1e0
fat_fill_super+0x2432/0x2880 fs/fat/inode.c:1888
vfat_fill_super+0x30/0x40 fs/fat/namei_vfat.c:1200
mount_bdev+0x152/0x1e0 fs/super.c:1659
vfat_mount+0x31/0x40 fs/fat/namei_vfat.c:1207
legacy_get_tree+0x77/0xd0 fs/fs_context.c:662
vfs_get_tree+0x56/0x1d0 fs/super.c:1780
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
x64_sys_call+0x25c9/0x2d70 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 0xffff88810e251000 of 1024 bytes by task 3306 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: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+0x126/0xaf0 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:2676
blkdev_read_iter+0x217/0x2c0 block/fops.c:749
new_sync_read fs/read_write.c:395 [inline]
vfs_read+0x5e6/0x6e0 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
x64_sys_call+0x27e5/0x2d70 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 PID: 3306 Comm: udevd Not tainted 6.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
==================================================================


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