[moderation] [exfat?] KCSAN: data-race in _copy_to_iter / fat32_ent_put (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8a9c6c40432e Merge tag 'io_uring-6.10-20240703' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=107e9bae980000
kernel config: https://syzkaller.appspot.com/x/.config?x=5b9537cd00be479e
dashboard link: https://syzkaller.appspot.com/bug?extid=6da9a8cbe8a05dfe7160
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/f01153f3ec8e/disk-8a9c6c40.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/04b88663a824/vmlinux-8a9c6c40.xz
kernel image: https://storage.googleapis.com/syzbot-assets/63c518cc63c5/bzImage-8a9c6c40.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6da9a8...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in _copy_to_iter / fat32_ent_put

read-write to 0xffff888126d2904c of 4 bytes by task 6731 on cpu 1:
fat32_ent_put+0x50/0x90 fs/fat/fatent.c:191
fat_ent_write+0x66/0xe0 fs/fat/fatent.c:417
fat_chain_add+0x15f/0x400 fs/fat/misc.c:136
fat_add_cluster fs/fat/inode.c:113 [inline]
__fat_get_block fs/fat/inode.c:155 [inline]
fat_get_block+0x46b/0x5e0 fs/fat/inode.c:190
__block_write_begin_int+0x417/0xfa0 fs/buffer.c:2128
__block_write_begin fs/buffer.c:2177 [inline]
block_write_begin+0x7b/0x170 fs/buffer.c:2236
cont_write_begin+0x486/0x6b0 fs/buffer.c:2590
fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
generic_perform_write+0x1d5/0x410 mm/filemap.c:4015
__generic_file_write_iter+0xa1/0x120 mm/filemap.c:4110
generic_file_write_iter+0x7d/0x1d0 mm/filemap.c:4136
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0x78f/0x900 fs/read_write.c:590
ksys_write+0xeb/0x1b0 fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__x64_sys_write+0x42/0x50 fs/read_write.c:652
x64_sys_call+0x27ef/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:2
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 0xffff888126d29000 of 1024 bytes by task 3160 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+0x126/0xaf0 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+0x5e9/0x6e0 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: 0 PID: 3160 Comm: udevd Not tainted 6.10.0-rc6-syzkaller-00067-g8a9c6c40432e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================


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