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: 6d23h, last: 6d23h
▶ ▼ ✨ 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
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Title Replies (including bot) Last reply
[syzbot] [jfs?] KASAN: slab-use-after-free Read in lmLog 0 (1) 2026/08/04 01:44

Sample crash report:
loop4: 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 ffff8880407c2150 by task syz.4.88/6240

CPU: 1 UID: 0 PID: 6240 Comm: syz.4.88 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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:5842
 __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_getdents64 fs/readdir.c:399 [inline]
 __se_sys_getdents64+0xf1/0x280 fs/readdir.c:384
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fae48cedf99
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:00007fae46f25028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007fae48f76090 RCX: 00007fae48cedf99
RDX: 0000000000001000 RSI: 0000200000000f80 RDI: 0000000000000005
RBP: 00007fae48d84ec4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fae48f76128 R14: 00007fae48f76090 R15: 00007ffcffa6fbb8
 </TASK>

Allocated by task 6240:
 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+0x3d2/0x6b0 mm/slub.c:5489
 _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:1640
 vfs_get_tree+0x92/0x2a0 fs/super.c:1700
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3765 [inline]
 do_new_mount+0x319/0xdc0 fs/namespace.c:3841
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4367
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6236:
 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:2677 [inline]
 slab_free mm/slub.c:6377 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6692
 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:1020
 do_remount fs/namespace.c:3407 [inline]
 path_mount+0xd4b/0x1040 fs/namespace.c:4153
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4367
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880407c2000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 336 bytes inside of
 freed 1024-byte region [ffff8880407c2000, ffff8880407c2400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x407c0
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 ffff88813ffb1dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813ffb1dc0 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 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5594, tgid 5594 (syz-executor), ts 77840044934, free_ts 75572931790
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x262a/0x26a0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3266 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3380
 new_slab mm/slub.c:3426 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7310
 refill_sheaf mm/slub.c:2804 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4675
 alloc_from_pcs mm/slub.c:4773 [inline]
 slab_alloc_node mm/slub.c:4905 [inline]
 __do_kmalloc_node mm/slub.c:5333 [inline]
 __kmalloc_noprof+0x544/0x780 mm/slub.c:5359
 _kmalloc_noprof include/linux/slab.h:992 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 tomoyo_init_log+0x1aaf/0x1fa0 security/tomoyo/audit.c:273
 tomoyo_supervisor+0x35f/0x1560 security/tomoyo/common.c:2232
 tomoyo_audit_path_number_log security/tomoyo/file.c:239 [inline]
 tomoyo_path_number_perm+0x463/0x5f0 security/tomoyo/file.c:739
 security_path_chmod+0x132/0x330 security/security.c:1581
 chmod_common+0x1a7/0x480 fs/open.c:632
 do_fchmodat+0x12d/0x230 fs/open.c:682
 __do_sys_chmod fs/open.c:706 [inline]
 __se_sys_chmod fs/open.c:704 [inline]
 __x64_sys_chmod+0x62/0x70 fs/open.c:704
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 1201 tgid 1201 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x10e7/0x11c0 mm/page_alloc.c:2950
 __folio_put+0x30f/0x3c0 mm/swap.c:112
 folio_put include/linux/mm.h:2124 [inline]
 put_page include/linux/mm.h:2193 [inline]
 put_netmem include/net/netmem.h:394 [inline]
 skb_page_unref include/linux/skbuff_ref.h:43 [inline]
 __skb_frag_unref include/linux/skbuff_ref.h:56 [inline]
 skb_release_data+0x573/0xab0 net/core/skbuff.c:1110
 skb_release_all net/core/skbuff.c:1191 [inline]
 __kfree_skb+0x5d/0x210 net/core/skbuff.c:1205
 tcp_clean_rtx_queue net/ipv4/tcp_input.c:3698 [inline]
 tcp_ack+0x28f7/0x8050 net/ipv4/tcp_input.c:4400
 tcp_rcv_established+0x1527/0x2910 net/ipv4/tcp_input.c:6589
 tcp_v4_do_rcv+0x959/0x13f0 net/ipv4/tcp_ipv4.c:1854
 tcp_v4_rcv+0x27d4/0x3170 net/ipv4/tcp_ipv4.c:2248
 ip_protocol_deliver_rcu+0x21d/0x440 net/ipv4/ip_input.c:207
 ip_local_deliver_finish+0x3bb/0x6f0 net/ipv4/ip_input.c:241
 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
 dst_input include/net/dst.h:481 [inline]
 ip_sublist_rcv_finish+0x1f0/0x240 net/ipv4/ip_input.c:623
 ip_list_rcv_finish net/ipv4/ip_input.c:675 [inline]
 ip_sublist_rcv+0x767/0xa70 net/ipv4/ip_input.c:683
 ip_list_rcv+0x3ec/0x440 net/ipv4/ip_input.c:717
 __netif_receive_skb_list_ptype net/core/dev.c:6256 [inline]
 __netif_receive_skb_list_core+0x804/0x830 net/core/dev.c:6302
 __netif_receive_skb_list net/core/dev.c:6354 [inline]
 netif_receive_skb_list_internal+0x995/0xcf0 net/core/dev.c:6445

Memory state around the buggy address:
 ffff8880407c2000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880407c2080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880407c2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff8880407c2180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880407c2200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.