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KASAN: slab-use-after-free Write in lmLogSync

Status: upstream: reported on 2026/06/02 10:40
Subsystems: jfs
Labels: actionable prio:high
[Documentation on labels]
Reported-by: syzbot+ea7ed3bb2f444cb4dfeb@syzkaller.appspotmail.com
First crash: 8d12h, last: 8d12h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
9069aaee-7687-48b8-ac43-e5386ccfd93a assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Write in lmLogSync 2026/06/02 09:58 2026/06/02 09:58 2026/06/02 10:50 1095583bae1d2729a3b4be301cb6ddc85ced9e38
9af09247-1fc4-499e-a8e8-961923ca5fa5 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Write in lmLogSync 2026/06/02 09:54 2026/06/02 09:54 2026/06/02 10:39 1095583bae1d2729a3b4be301cb6ddc85ced9e38
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [jfs?] KASAN: slab-use-after-free Write in lmLogSync 0 (1) 2026/06/02 10:40
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in lmLogSync (2) jfs 22 C error 8238 15d 1341d 29/29 fixed on 2026/05/21 07:49
linux-6.6 general protection fault in lmLogSync origin:upstream missing-backport 22 C error 205 13h44m 346d 0/2 upstream: reported C repro on 2025/06/21 09:37
linux-6.1 BUG: unable to handle kernel paging request in lmLogSync origin:upstream 22 C 1128 5h28m 1176d 0/3 upstream: reported C repro on 2023/03/14 01:30
linux-5.15 BUG: unable to handle kernel paging request in lmLogSync missing-backport origin:upstream 22 C error 627 4d09h 1176d 0/3 upstream: reported C repro on 2023/03/14 00:56
upstream general protection fault in lmLogSync jfs 2 1 1516d 1504d 0/29 auto-closed as invalid on 2022/08/06 08:08

Sample crash report:
 ... Log Wrap ... Log Wrap ... Log Wrap ...
==================================================================
BUG: KASAN: slab-use-after-free in lmLogSync+0x794/0x7b0 fs/jfs/jfs_logmgr.c:1003
Write of size 4 at addr ffff88807d709218 by task jfsCommit/117

CPU: 0 UID: 0 PID: 117 Comm: jfsCommit Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1d0 mm/kasan/report.c:595
 lmLogSync+0x794/0x7b0 fs/jfs/jfs_logmgr.c:1003
 jfs_syncpt+0x89/0xa0 fs/jfs/jfs_logmgr.c:1039
 txEnd+0x318/0x490 fs/jfs/jfs_txnmgr.c:551
 txLazyCommit fs/jfs/jfs_txnmgr.c:2686 [inline]
 jfs_lazycommit+0x748/0xab0 fs/jfs/jfs_txnmgr.c:2735
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 15951:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 open_inline_log fs/jfs/jfs_logmgr.c:1157 [inline]
 lmLogOpen+0x571/0x1360 fs/jfs/jfs_logmgr.c:1067
 jfs_mount_rw+0x2e0/0x690 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0xbc0/0xf50 fs/jfs/super.c:532
 get_tree_bdev_flags+0x38c/0x620 fs/super.c:1694
 vfs_get_tree+0x92/0x320 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount fs/namespace.c:3834 [inline]
 path_mount+0x7d0/0x23d0 fs/namespace.c:4154
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount fs/namespace.c:4360 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:4360
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0x860 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 10281:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/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:6251 [inline]
 kfree+0x223/0x6c0 mm/slub.c:6566
 lmLogClose+0x55f/0x6f0 fs/jfs/jfs_logmgr.c:1458
 jfs_umount+0x30c/0x430 fs/jfs/jfs_umount.c:124
 jfs_put_super+0x88/0x1a0 fs/jfs/super.c:194
 generic_shutdown_super+0x167/0x360 fs/super.c:646
 kill_block_super+0x3b/0xa0 fs/super.c:1725
 deactivate_locked_super+0xc1/0x1b0 fs/super.c:476
 deactivate_super fs/super.c:509 [inline]
 deactivate_super+0xe7/0x110 fs/super.c:505
 cleanup_mnt+0x21f/0x450 fs/namespace.c:1312
 task_work_run+0x150/0x240 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+0x107/0x4f0 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:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x706/0x860 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807d709000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 536 bytes inside of
 freed 1024-byte region [ffff88807d709000, ffff88807d709400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88807d70d000 pfn:0x7d708
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff88813fe34dc0 ffffea0001ddac10 ffffea0001e99e10
raw: ffff88807d70d000 000000080010000e 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fe34dc0 ffffea0001ddac10 ffffea0001e99e10
head: ffff88807d70d000 000000080010000e 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 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 5636, tgid 5636 (syz-executor), ts 92244588377, free_ts 92228867410
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7272
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4652
 alloc_from_pcs mm/slub.c:4750 [inline]
 slab_alloc_node mm/slub.c:4884 [inline]
 __do_kmalloc_node mm/slub.c:5295 [inline]
 __kvmalloc_node_noprof+0x7da/0xa00 mm/slub.c:6833
 bucket_table_alloc.isra.0+0x88/0x460 lib/rhashtable.c:194
 rhashtable_init_noprof+0x43b/0x890 lib/rhashtable.c:1108
 ipc_init_ids+0x92/0x280 ipc/util.c:120
 create_ipc_ns ipc/namespace.c:89 [inline]
 copy_ipcs+0x5c8/0x7e0 ipc/namespace.c:116
 create_new_namespaces+0x20a/0xac0 kernel/nsproxy.c:112
 unshare_nsproxy_namespaces+0xf2/0x220 kernel/nsproxy.c:234
 ksys_unshare+0x438/0xab0 kernel/fork.c:3243
 __do_sys_unshare kernel/fork.c:3317 [inline]
 __se_sys_unshare kernel/fork.c:3315 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:3315
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0x860 arch/x86/entry/syscall_64.c:94
page last free pid 5646 tgid 5646 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4570 [inline]
 slab_alloc_node mm/slub.c:4899 [inline]
 __kmalloc_cache_noprof+0x243/0x6f0 mm/slub.c:5415
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 hci_chan_create+0xa6/0x410 net/bluetooth/hci_conn.c:2874
 l2cap_conn_add.part.0+0x1a/0xb00 net/bluetooth/l2cap_core.c:6997
 l2cap_conn_add net/bluetooth/l2cap_core.c:69 [inline]
 l2cap_connect_cfm+0x43e/0xf80 net/bluetooth/l2cap_core.c:7378
 hci_connect_cfm include/net/bluetooth/hci_core.h:2139 [inline]
 le_conn_complete_evt+0x197c/0x1f60 net/bluetooth/hci_event.c:5865
 hci_le_conn_complete_evt+0x23c/0x3a0 net/bluetooth/hci_event.c:5891
 hci_le_meta_evt+0x34a/0x5f0 net/bluetooth/hci_event.c:7529
 hci_event_func net/bluetooth/hci_event.c:7793 [inline]
 hci_event_packet+0x51c/0xcd0 net/bluetooth/hci_event.c:7847
 hci_rx_work+0x451/0xfc0 net/bluetooth/hci_core.c:4077
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314
 process_scheduled_works kernel/workqueue.c:3397 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478
 kthread+0x370/0x450 kernel/kthread.c:436

Memory state around the buggy address:
 ffff88807d709100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807d709180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807d709200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88807d709280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807d709300: 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
2026/05/24 22:48 upstream 6a97c4d5262d c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root KASAN: slab-use-after-free Write in lmLogSync
* Struck through repros no longer work on HEAD.