[moderation] [exfat?] KCSAN: data-race in _copy_to_iter / fat16_ent_put (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: feffde684ac2 Merge tag 'for-6.13-rc1-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=148e8020580000
kernel config: https://syzkaller.appspot.com/x/.config?x=5337d87dae437af8
dashboard link: https://syzkaller.appspot.com/bug?extid=30fe4109d2d73abfcb59
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/07bd7dab67c2/disk-feffde68.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/98e4eb1e864c/vmlinux-feffde68.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b8b7890995ec/bzImage-feffde68.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+30fe41...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in _copy_to_iter / fat16_ent_put

write to 0xffff88813dc7d3ee of 2 bytes by task 30096 on cpu 1:
fat16_ent_put+0x28/0x60 fs/fat/fatent.c:183
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:112 [inline]
__fat_get_block fs/fat/inode.c:154 [inline]
fat_get_block+0x46b/0x5e0 fs/fat/inode.c:189
__block_write_begin_int+0x417/0xfa0 fs/buffer.c:2116
block_write_begin fs/buffer.c:2226 [inline]
cont_write_begin+0x546/0x860 fs/buffer.c:2577
fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
cont_expand_zero fs/buffer.c:2504 [inline]
cont_write_begin+0x18b/0x860 fs/buffer.c:2567
fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
generic_cont_expand_simple+0xaa/0x150 fs/buffer.c:2468
fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
fat_setattr+0x2aa/0x840 fs/fat/file.c:513
notify_change+0x85c/0x8e0 fs/attr.c:552
do_truncate fs/open.c:65 [inline]
do_ftruncate+0x3cf/0x460 fs/open.c:181
do_sys_ftruncate fs/open.c:196 [inline]
__do_sys_ftruncate fs/open.c:201 [inline]
__se_sys_ftruncate fs/open.c:199 [inline]
__x64_sys_ftruncate+0x67/0xc0 fs/open.c:199
x64_sys_call+0x9d9/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:78
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 0xffff88813dc7d000 of 1024 bytes by task 12137 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+0x130/0xd00 lib/iov_iter.c:185
copy_page_to_iter+0x171/0x2b0 lib/iov_iter.c:362
copy_folio_to_iter include/linux/uio.h:189 [inline]
filemap_read+0x42d/0x6a0 mm/filemap.c:2697
blkdev_read_iter+0x20e/0x2c0 block/fops.c:770
new_sync_read fs/read_write.c:484 [inline]
vfs_read+0x5dc/0x700 fs/read_write.c:565
ksys_read+0xe8/0x1b0 fs/read_write.c:708
__do_sys_read fs/read_write.c:717 [inline]
__se_sys_read fs/read_write.c:715 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:715
x64_sys_call+0x2874/0x2dc0 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 UID: 0 PID: 12137 Comm: udevd Tainted: G W 6.13.0-rc1-syzkaller-00025-gfeffde684ac2 #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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