[moderation] [mm?] KCSAN: data-race in _copy_to_iter / copy_page_from_iter_atomic (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d07de43e3f05 Merge tag 'io_uring-6.14-20250321' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1337d004580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f33d372c4021745
dashboard link: https://syzkaller.appspot.com/bug?extid=83b7700a21985430f469
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ak...@linux-foundation.org hu...@google.com linux-...@vger.kernel.org linu...@kvack.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a651863e3a8e/disk-d07de43e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f70bdebf17a0/vmlinux-d07de43e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fadd3249ef09/bzImage-d07de43e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+83b770...@syzkaller.appspotmail.com

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

write to 0xffff88818ab6d000 of 4096 bytes by task 14686 on cpu 0:
instrument_copy_from_user_before include/linux/instrumented.h:130 [inline]
copy_from_user_iter lib/iov_iter.c:54 [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_from_iter lib/iov_iter.c:249 [inline]
copy_page_from_iter_atomic+0x28d/0xf80 lib/iov_iter.c:483
copy_folio_from_iter_atomic include/linux/uio.h:210 [inline]
generic_perform_write+0x2d0/0x4a0 mm/filemap.c:4120
shmem_file_write_iter+0xc2/0xe0 mm/shmem.c:3477
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0x77b/0x920 fs/read_write.c:679
ksys_write+0xe8/0x1b0 fs/read_write.c:731
__do_sys_write fs/read_write.c:742 [inline]
__se_sys_write fs/read_write.c:739 [inline]
__x64_sys_write+0x42/0x50 fs/read_write.c:739
x64_sys_call+0x287e/0x2dc0 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 0xffff88818ab6d000 of 4096 bytes by task 14903 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: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:198 [inline]
shmem_file_read_iter+0x2c1/0x540 mm/shmem.c:3425
new_sync_read fs/read_write.c:484 [inline]
vfs_read+0x5cc/0x6f0 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: 1 UID: 0 PID: 14903 Comm: syz.5.23390 Not tainted 6.14.0-rc7-syzkaller-00186-gd07de43e3f05 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================


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[syzbot]

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