[moderation] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4774cfe3543a Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1466de0c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=cb55ce02d42a1797
dashboard link: https://syzkaller.appspot.com/bug?extid=fbb1878f62250eb4111f
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
CC: [ak...@linux-foundation.org baoli...@linux.alibaba.com 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/97bb82d143d5/disk-4774cfe3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/705549b5d0ef/vmlinux-4774cfe3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/49a4d858182e/bzImage-4774cfe3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fbb187...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in memcpy_from_iter lib/iov_iter.c:73 [inline]
BUG: KASAN: use-after-free in iterate_bvec include/linux/iov_iter.h:123 [inline]
BUG: KASAN: use-after-free in iterate_and_advance2 include/linux/iov_iter.h:304 [inline]
BUG: KASAN: use-after-free in iterate_and_advance include/linux/iov_iter.h:328 [inline]
BUG: KASAN: use-after-free in __copy_from_iter lib/iov_iter.c:249 [inline]
BUG: KASAN: use-after-free in copy_folio_from_iter_atomic+0xb0b/0x18f0 lib/iov_iter.c:479
Read of size 4096 at addr ffff888028343000 by task kworker/u8:6/1164

CPU: 0 UID: 0 PID: 1164 Comm: kworker/u8:6 Not tainted 6.16.0-rc1-syzkaller-00203-g4774cfe3543a #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: loop3 loop_workfn
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:408 [inline]
print_report+0xd2/0x2b0 mm/kasan/report.c:521
kasan_report+0x118/0x150 mm/kasan/report.c:634
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:189
__asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
memcpy_from_iter lib/iov_iter.c:73 [inline]
iterate_bvec include/linux/iov_iter.h:123 [inline]
iterate_and_advance2 include/linux/iov_iter.h:304 [inline]
iterate_and_advance include/linux/iov_iter.h:328 [inline]
__copy_from_iter lib/iov_iter.c:249 [inline]
copy_folio_from_iter_atomic+0xb0b/0x18f0 lib/iov_iter.c:479
generic_perform_write+0x5f1/0x910 mm/filemap.c:4130
shmem_file_write_iter+0xf8/0x120 mm/shmem.c:3463
lo_rw_aio+0xd8e/0x1040 include/linux/percpu-rwsem.h:-1
do_req_filebacked drivers/block/loop.c:-1 [inline]
loop_handle_cmd drivers/block/loop.c:1890 [inline]
loop_process_work+0x810/0xf40 drivers/block/loop.c:1925
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3321
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888028343dc0 pfn:0x28343
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea000131e7c8 ffffea00013e2b88 0000000000000000
raw: ffff888028343dc0 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xdc0(GFP_KERNEL|__GFP_ZERO), pid 7082, tgid 7081 (syz.3.105), ts 179934796567, free_ts 181794245819
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
prep_new_page mm/page_alloc.c:1712 [inline]
get_page_from_freelist+0x21d5/0x22b0 mm/page_alloc.c:3669
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
alloc_frozen_pages_noprof mm/mempolicy.c:2490 [inline]
alloc_pages_noprof+0xa9/0x190 mm/mempolicy.c:2510
lbmLogInit fs/jfs/jfs_logmgr.c:1816 [inline]
lmLogInit+0x332/0x19e0 fs/jfs/jfs_logmgr.c:1270
open_inline_log fs/jfs/jfs_logmgr.c:1175 [inline]
lmLogOpen+0x4e1/0xfb0 fs/jfs/jfs_logmgr.c:1069
jfs_mount_rw+0xe9/0x670 fs/jfs/jfs_mount.c:257
jfs_fill_super+0x754/0xd90 fs/jfs/super.c:532
get_tree_bdev_flags+0x40b/0x4d0 fs/super.c:1679
vfs_get_tree+0x92/0x2b0 fs/super.c:1802
do_new_mount+0x24a/0xa40 fs/namespace.c:3885
do_mount fs/namespace.c:4222 [inline]
__do_sys_mount fs/namespace.c:4433 [inline]
__se_sys_mount+0x317/0x410 fs/namespace.c:4410
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5834 tgid 5834 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1248 [inline]
__free_frozen_pages+0xc65/0xe60 mm/page_alloc.c:2706
lbmLogShutdown fs/jfs/jfs_logmgr.c:1864 [inline]
lmLogShutdown+0x439/0x830 fs/jfs/jfs_logmgr.c:1684
lmLogClose+0x28a/0x520 fs/jfs/jfs_logmgr.c:1460
jfs_umount+0x2ef/0x3c0 fs/jfs/jfs_umount.c:114
jfs_put_super+0x8c/0x190 fs/jfs/super.c:194
generic_shutdown_super+0x135/0x2c0 fs/super.c:643
kill_block_super+0x44/0x90 fs/super.c:1753
deactivate_locked_super+0xb9/0x130 fs/super.c:474
cleanup_mnt+0x425/0x4c0 fs/namespace.c:1417
task_work_run+0x1d1/0x260 kernel/task_work.c:227
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:114
exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff888028342f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888028342f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888028343000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff888028343080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888028343100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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[Aleksandr Nogikh]

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[syzbot]

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