KASAN: slab-use-after-free Read in lmLog

Status: upstream: reported on 2026/08/04 01:44
Subsystems: jfs
Labels: prio:normal actionable
[Documentation on labels]
Reported-by: syzbot+5e630048345c54c4d7f4@syzkaller.appspotmail.com
First crash: 53d, last: 31d
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
c8d86e21 repro-c Reproduced: ✅ ❓ KASAN: slab-use-after-free Read in lmLog 2026/08/05 15:00 2026/08/05 15:00 2026/08/05 19:28 e33390b8
5ba37477 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in lmLog 2026/08/04 01:06 2026/08/04 01:06 2026/08/04 01:44 cb1adeae
07e49de8 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in lmLog 2026/08/01 01:58 2026/08/01 01:58 2026/08/01 02:35 7664cf44
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [jfs?] KASAN: slab-use-after-free Read in lmLog 0 (1) 2026/08/04 01:44
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/08/06 07:08 20m glider@google.com upstream report log

Sample crash report:
loop3: detected capacity change from 0 to 32768
add_index: next_index = 0.  Resetting!
==================================================================
BUG: KASAN: slab-use-after-free in __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline]
BUG: KASAN: slab-use-after-free in mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578
Read of size 1 at addr ffff88803213d150 by task syz.3.998/16357

CPU: 0 UID: 0 PID: 16357 Comm: syz.3.998 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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
 __kasan_check_byte+0x2a/0x40 mm/kasan/common.c:574
 kasan_check_byte include/linux/kasan.h:402 [inline]
 lock_acquire+0x84/0x350 kernel/locking/lockdep.c:5860
 __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578
 lmLog+0x78/0xa10 fs/jfs/jfs_logmgr.c:234
 dtLog fs/jfs/jfs_txnmgr.c:1620 [inline]
 txLog fs/jfs/jfs_txnmgr.c:1402 [inline]
 txCommit+0x1c92/0x54a0 fs/jfs/jfs_txnmgr.c:1266
 add_missing_indices+0x7e5/0xb30 fs/jfs/jfs_dtree.c:2671
 jfs_readdir+0x1d15/0x33f0 fs/jfs/jfs_dtree.c:3028
 wrap_directory_iterator+0x99/0xe0 fs/readdir.c:67
 iterate_dir+0x2f1/0x4e0 fs/readdir.c:110
 __do_sys_getdents fs/readdir.c:319 [inline]
 __se_sys_getdents+0xf1/0x270 fs/readdir.c:304
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5b0af8e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5b091c5028 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f5b0b216090 RCX: 00007f5b0af8e0d9
RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000006
RBP: 00007f5b0b025024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5b0b216128 R14: 00007f5b0b216090 R15: 00007fff967b08e8
 </TASK>

Allocated by task 16357:
 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+0x3da/0x6b0 mm/slub.c:5484
 _kmalloc_noprof include/linux/slab.h:988 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 open_inline_log fs/jfs/jfs_logmgr.c:1157 [inline]
 lmLogOpen+0x2d1/0xf90 fs/jfs/jfs_logmgr.c:1067
 jfs_mount_rw+0xf3/0x670 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0x769/0xda0 fs/jfs/super.c:533
 get_tree_bdev_flags+0x430/0x4f0 fs/super.c:1887
 vfs_get_tree+0x92/0x2a0 fs/super.c:1947
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3772 [inline]
 do_new_mount+0x319/0xdc0 fs/namespace.c:3848
 do_mount fs/namespace.c:4181 [inline]
 __do_sys_mount fs/namespace.c:4397 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4374
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 16355:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 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:2678 [inline]
 slab_free mm/slub.c:6372 [inline]
 kfree+0x1c5/0x6d0 mm/slub.c:6687
 lmLogClose+0x296/0x530 fs/jfs/jfs_logmgr.c:-1
 jfs_reconfigure+0x6d3/0x990 fs/jfs/super.c:421
 reconfigure_super+0x232/0x8f0 fs/super.c:1143
 do_remount fs/namespace.c:3410 [inline]
 path_mount+0xd4e/0x1050 fs/namespace.c:4160
 do_mount fs/namespace.c:4181 [inline]
 __do_sys_mount fs/namespace.c:4397 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4374
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88803213d000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 336 bytes inside of
 freed 1024-byte region [ffff88803213d000, ffff88803213d400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x32138
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813ffb5dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813ffb5dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0080000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5858, tgid 5856 (syz.3.14), ts 99720688601
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x2591/0x2600 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x230/0x5c0 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3267 [inline]
 allocate_slab+0x7c/0x5e0 mm/slub.c:3382
 new_slab mm/slub.c:3428 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7305
 refill_sheaf mm/slub.c:2805 [inline]
 __pcs_replace_empty_main+0x334/0x690 mm/slub.c:4677
 alloc_from_pcs mm/slub.c:4775 [inline]
 slab_alloc_node mm/slub.c:4907 [inline]
 __kmalloc_cache_noprof+0x470/0x6b0 mm/slub.c:5480
 _kmalloc_noprof include/linux/slab.h:988 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 io_uring_alloc_task_context+0xa2/0x6c0 io_uring/tctx.c:88
 __io_uring_add_tctx_node+0x48d/0x630 io_uring/tctx.c:152
 io_uring_create+0x596/0x990 io_uring/io_uring.c:3066
 io_uring_setup io_uring/io_uring.c:3111 [inline]
 __do_sys_io_uring_setup io_uring/io_uring.c:3145 [inline]
 __se_sys_io_uring_setup+0x2a8/0x2c0 io_uring/io_uring.c:3136
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5786 tgid 5786 ts 99693822519 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0xf8e/0x1070 mm/page_alloc.c:2962
 __slab_free+0x252/0x2a0 mm/slub.c:5736
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4586 [inline]
 slab_alloc_node mm/slub.c:4919 [inline]
 kmem_cache_alloc_node_noprof+0x3f3/0x670 mm/slub.c:4991
 __alloc_skb+0x1db/0x7a0 net/core/skbuff.c:704
 alloc_skb include/linux/skbuff.h:1384 [inline]
 mld_newpack+0x165/0xcb0 net/ipv6/mcast.c:1790
 add_grhead net/ipv6/mcast.c:1901 [inline]
 add_grec+0x119f/0x19d0 net/ipv6/mcast.c:2040
 mld_send_initial_cr+0x288/0x550 net/ipv6/mcast.c:2285
 mld_dad_work+0x3d/0x480 net/ipv6/mcast.c:2311
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
 kthread+0x38b/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

Memory state around the buggy address:
 ffff88803213d000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803213d080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88803213d100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88803213d180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803213d200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/22 05:29 upstream 818bebeb63dd 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in lmLog
2026/07/30 05:59 upstream fc46aed51f62 6ef5c1e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in lmLog
* Struck through repros no longer work on HEAD.