[syzbot] [erofs?] KASAN: global-out-of-bounds Read in z_erofs_decompress_queue

[syzbot <syzbot+5a398eb460ddaa6f242f@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    3957a5720157 Merge tag 'cgroup-for-6.17-rc2-fixes' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=104f0062580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e1e1566c7726877e
dashboard link: https://syzkaller.appspot.com/bug?extid=5a398eb460ddaa6f242f
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16650c42580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1277dfa2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c5cbe8650b9a/disk-3957a572.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/51911bea9855/vmlinux-3957a572.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b07279b5fcc2/bzImage-3957a572.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/b6ca0d9a661b/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=142187bc580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5a398eb460ddaa6f242f@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in z_erofs_decompress_pcluster fs/erofs/zdata.c:1274 [inline]
BUG: KASAN: global-out-of-bounds in z_erofs_decompress_queue+0x341/0x3580 fs/erofs/zdata.c:1411
Read of size 8 at addr ffffffff8e05df10 by task kworker/u9:1/5152

CPU: 1 UID: 0 PID: 5152 Comm: kworker/u9:1 Tainted: G        W           syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: erofs_worker z_erofs_decompressqueue_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 z_erofs_decompress_pcluster fs/erofs/zdata.c:1274 [inline]
 z_erofs_decompress_queue+0x341/0x3580 fs/erofs/zdata.c:1411
 z_erofs_decompressqueue_work+0x82/0xd0 fs/erofs/zdata.c:1423
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 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 variable:
 z_erofs_decomp+0x30/0xe0

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xe05d
flags: 0x80000000002000(reserved|node=0|zone=1)
raw: 0080000000002000 ffffea0000381748 ffffea0000381748 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffffffff8e05de00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff8e05de80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff8e05df00: 00 00 f9 f9 f9 f9 f9 f9 00 00 00 00 00 00 00 00
                         ^
 ffffffff8e05df80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff8e05e000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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