[syzbot] [erofs?] KASAN: use-after-free Read in z_erofs_transform_plain (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8bf22c33e7a1 Merge tag 'net-7.0-rc1' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=178f7ffa580000
kernel config: https://syzkaller.appspot.com/x/.config?x=abe4fa590468dbfb
dashboard link: https://syzkaller.appspot.com/bug?extid=d988dc155e740d76a331
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=157fb95a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=102a9722580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/010f0532c934/disk-8bf22c33.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ed0946db3f63/vmlinux-8bf22c33.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ef1efd866885/bzImage-8bf22c33.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/ca3875f86433/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1450c73a580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d988dc...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy_to_page include/linux/highmem.h:552 [inline]
BUG: KASAN: slab-out-of-bounds in z_erofs_transform_plain+0x33c/0xa00 fs/erofs/decompressor.c:309
Read of size 4096 at addr ffff88803f175800 by task kworker/u9:2/5851

CPU: 1 UID: 0 PID: 5851 Comm: kworker/u9:2 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: erofs_worker z_erofs_decompressqueue_work
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xba/0x230 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
__asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
memcpy_to_page include/linux/highmem.h:552 [inline]
z_erofs_transform_plain+0x33c/0xa00 fs/erofs/decompressor.c:309
z_erofs_decompress_pcluster fs/erofs/zdata.c:1297 [inline]
z_erofs_decompress_queue+0x1af7/0x3740 fs/erofs/zdata.c:1410
z_erofs_decompressqueue_work+0x88/0xe0 fs/erofs/zdata.c:1422
process_one_work kernel/workqueue.c:3275 [inline]
process_scheduled_works+0xb02/0x1830 kernel/workqueue.c:3358
worker_thread+0xa50/0xfc0 kernel/workqueue.c:3439
kthread+0x388/0x470 kernel/kthread.c:467
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88803f175900 pfn:0x3f175
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 0000000000000000 dead000000000122 0000000000000000
raw: ffff88803f175900 fffffffffffffffc 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xc40(GFP_NOFS), pid 6046, tgid 6046 (syz.1.18), ts 99298614076, free_ts 99297784595
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x28bb/0x2950 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2485
alloc_frozen_pages_noprof mm/mempolicy.c:2556 [inline]
alloc_pages_noprof+0xce/0x1e0 mm/mempolicy.c:2576
__erofs_allocpage+0x1a0/0x270 fs/erofs/zutil.c:190
z_erofs_fill_bio_vec fs/erofs/zdata.c:1560 [inline]
z_erofs_submit_queue fs/erofs/zdata.c:1728 [inline]
z_erofs_runqueue+0xb2f/0x20f0 fs/erofs/zdata.c:1808
z_erofs_readahead+0x8ad/0xc10 fs/erofs/zdata.c:1936
read_pages+0x193/0x5a0 mm/readahead.c:163
page_cache_ra_unbounded+0x704/0x9b0 mm/readahead.c:304
do_page_cache_ra mm/readahead.c:334 [inline]
page_cache_ra_order+0x2b5/0x4b0 mm/readahead.c:538
filemap_readahead mm/filemap.c:2658 [inline]
filemap_get_pages+0x832/0x1ea0 mm/filemap.c:2704
filemap_read+0x44a/0x1240 mm/filemap.c:2800
erofs_file_read_iter+0x249/0x2d0 fs/erofs/data.c:441
__kernel_read+0x50d/0x9c0 fs/read_write.c:532
integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
page last free pid 6046 tgid 6046 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0xfe3/0x1170 mm/page_alloc.c:2978
__folio_put+0x25d/0x310 mm/swap.c:112
erofs_release_pages+0x1c9/0x270 fs/erofs/zutil.c:213
z_erofs_decompressqueue_work fs/erofs/zdata.c:1423 [inline]
z_erofs_decompress_kickoff+0x2aa/0x330 fs/erofs/zdata.c:1480
z_erofs_submit_queue fs/erofs/zdata.c:1791 [inline]
z_erofs_runqueue+0x1db8/0x20f0 fs/erofs/zdata.c:1808
z_erofs_readahead+0x8ad/0xc10 fs/erofs/zdata.c:1936
read_pages+0x193/0x5a0 mm/readahead.c:163
page_cache_ra_unbounded+0x704/0x9b0 mm/readahead.c:304
do_page_cache_ra mm/readahead.c:334 [inline]
page_cache_ra_order+0x2b5/0x4b0 mm/readahead.c:538
filemap_get_pages+0x47c/0x1ea0 mm/filemap.c:2690
filemap_read+0x44a/0x1240 mm/filemap.c:2800
erofs_file_read_iter+0x249/0x2d0 fs/erofs/data.c:441
__kernel_read+0x50d/0x9c0 fs/read_write.c:532
integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:480 [inline]
ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
ima_calc_file_hash+0x12cf/0x1800 security/integrity/ima/ima_crypto.c:568
ima_collect_measurement+0x491/0x930 security/integrity/ima/ima_api.c:294

Memory state around the buggy address:
ffff88803f175f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88803f176000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88803f176080: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc 00 00
^
ffff88803f176100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88803f176180: 00 00 00 00 fc fc fc fc fc fc fc fc 00 00 00 00
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup