Re: [syzbot] [jfs?] KASAN: slab-use-after-free Read in lbmIODone

syzbot
2026-04-15T09:06:32Z

syzbot has found a reproducer for the following issue on:

HEAD commit: e6efabc0afca Add linux-next specific files for 20260414
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17ee18ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=56c2b36de3316f1b
dashboard link: https://syzkaller.appspot.com/bug?extid=ecf51a7ccb6b1394e90c
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=11dc01ba580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173bfb02580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e7099cbf73e4/disk-e6efabc0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/439c402df1b9/vmlinux-e6efabc0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc0c0175fc76/bzImage-e6efabc0.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/81df22d6836d/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=107dfcd2580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ecf51a7ccb6b1394e90c@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in lbmIODone+0x1312/0x16c0 fs/jfs/jfs_logmgr.c:2192
Read of size 4 at addr ffff88802a45a608 by task ksoftirqd/1/31

CPU: 1 UID: 0 PID: 31 Comm: ksoftirqd/1 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
lbmIODone+0x1312/0x16c0 fs/jfs/jfs_logmgr.c:2192
blk_update_request+0x57e/0xe60 block/blk-mq.c:1016
blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1178
blk_complete_reqs block/blk-mq.c:1253 [inline]
blk_done_softirq+0x10a/0x160 block/blk-mq.c:1258
handle_softirqs+0x1de/0x6d0 kernel/softirq.c:622
run_ksoftirqd+0x52/0x180 kernel/softirq.c:1076
smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

Allocated by task 6106:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x3a6/0x690 mm/slub.c:5415
kmalloc_noprof include/linux/slab.h:950 [inline]
lbmLogInit fs/jfs/jfs_logmgr.c:1819 [inline]
lmLogInit+0x3e5/0x1a00 fs/jfs/jfs_logmgr.c:1267
open_inline_log fs/jfs/jfs_logmgr.c:1173 [inline]
lmLogOpen+0x4e1/0xfa0 fs/jfs/jfs_logmgr.c:1067
jfs_mount_rw+0xee/0x670 fs/jfs/jfs_mount.c:257
jfs_fill_super+0x754/0xd80 fs/jfs/super.c:532
get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
vfs_get_tree+0x92/0x2a0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3758 [inline]
do_new_mount+0x341/0xd30 fs/namespace.c:3834
do_mount fs/namespace.c:4167 [inline]
__do_sys_mount fs/namespace.c:4399 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4376
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5969:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2689 [inline]
slab_free mm/slub.c:6246 [inline]
kfree+0x1c5/0x6c0 mm/slub.c:6561
lbmLogShutdown fs/jfs/jfs_logmgr.c:1862 [inline]
lmLogShutdown+0x456/0x850 fs/jfs/jfs_logmgr.c:1681
lmLogClose+0x28a/0x520 fs/jfs/jfs_logmgr.c:1457
jfs_umount+0x2fb/0x3d0 fs/jfs/jfs_umount.c:124
jfs_put_super+0x8c/0x190 fs/jfs/super.c:194
generic_shutdown_super+0x13d/0x2d0 fs/super.c:646
kill_block_super+0x44/0x90 fs/super.c:1725
deactivate_locked_super+0xbc/0x130 fs/super.c:476
cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312
task_work_run+0x1d9/0x270 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:328 [inline]
do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802a45a600
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 8 bytes inside of
freed 256-byte region [ffff88802a45a600, ffff88802a45a700)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2a45a
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88801a02cb40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88801a02cb40 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0080000000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 155, tgid 155 (kworker/u8:6), ts 12504727555, free_ts 0
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1858
prep_new_page mm/page_alloc.c:1866 [inline]
get_page_from_freelist+0x27d6/0x2850 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3467
new_slab mm/slub.c:3525 [inline]
refill_objects+0x33c/0x3d0 mm/slub.c:7251
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x373/0x720 mm/slub.c:4651
alloc_from_pcs mm/slub.c:4749 [inline]
slab_alloc_node mm/slub.c:4883 [inline]
__kmalloc_cache_noprof+0x44e/0x690 mm/slub.c:5410
kmalloc_noprof include/linux/slab.h:950 [inline]
scsi_probe_and_add_lun+0x2f8/0x48e0 drivers/scsi/scsi_scan.c:1225
__scsi_scan_target+0x1f0/0xe10 drivers/scsi/scsi_scan.c:1786
scsi_scan_channel drivers/scsi/scsi_scan.c:1874 [inline]
scsi_scan_host_selected+0x3d3/0x780 drivers/scsi/scsi_scan.c:1903
do_scsi_scan_host drivers/scsi/scsi_scan.c:2036 [inline]
do_scan_async+0x124/0x6f0 drivers/scsi/scsi_scan.c:2046
async_run_entry_fn+0xa8/0x440 kernel/async.c:129
process_one_work kernel/workqueue.c:3308 [inline]
process_scheduled_works+0xb68/0x1910 kernel/workqueue.c:3399
worker_thread+0xa90/0x1040 kernel/workqueue.c:3485
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
page_owner free stack trace missing

Memory state around the buggy address:
ffff88802a45a500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802a45a580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802a45a600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802a45a680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802a45a700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

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