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

Status: upstream: reported syz repro on 2026/06/02 10:40
Subsystems: jfs
Labels: actionable prio:high
[Documentation on labels]
Reported-by: syzbot+ea7ed3bb2f444cb4dfeb@syzkaller.appspotmail.com
First crash: 141d, last: 49d
Cause bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
9069aaee 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 1095583b
9af09247 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 1095583b
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[syzbot] [jfs?] KASAN: slab-use-after-free Write in lmLogSync 0 (2) 2026/06/25 19:01
[PATCH] jfs: fix use-after-free in lmLogSync during unmount 1 (1) 2026/06/03 17:16
▶ ▼ 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 syz, C error 8238 148d 1474d 29/29 fixed on 2026/05/21 07:49
linux-6.6 general protection fault in lmLogSync origin:upstream missing-backport 22 syz, C error 245 6d04h 479d 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 syz, C 1227 1d01h 1309d 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 syz, C error 658 12h31m 1309d 0/3 upstream: reported C repro on 2023/03/14 00:56
upstream general protection fault in lmLogSync jfs 2 1 1649d 1637d 0/29 auto-closed as invalid on 2022/08/06 08:08
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/10/04 04:06 25m retest repro upstream no crash job log log
2026/07/10 02:56 37m retest repro upstream log
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/07/25 19:44 2h33m bisect fix upstream OK (0) job log log

Sample crash report:
 ... Log Wrap ... Log Wrap ... Log Wrap ...
==================================================================
BUG: KASAN: slab-use-after-free in lmLogSync+0x9a5/0xa40 fs/jfs/jfs_logmgr.c:1003
Write of size 4 at addr ffff888030829a18 by task jfsCommit/117

CPU: 1 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 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
 lmLogSync+0x9a5/0xa40 fs/jfs/jfs_logmgr.c:1003
 jfs_syncpt+0x7b/0x90 fs/jfs/jfs_logmgr.c:1039
 txEnd+0x2e5/0x530 fs/jfs/jfs_txnmgr.c:551
 txLazyCommit fs/jfs/jfs_txnmgr.c:2686 [inline]
 jfs_lazycommit+0x5d6/0xac0 fs/jfs/jfs_txnmgr.c:2735
 kthread+0x38b/0x480 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 17571:
 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+0x321/0x600 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [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 14790:
 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:2748 [inline]
 slab_free mm/slub.c:6499 [inline]
 kfree+0x1c5/0x650 mm/slub.c:6792
 lmLogClose+0x296/0x530 fs/jfs/jfs_logmgr.c:-1
 jfs_umount+0x2da/0x3b0 fs/jfs/jfs_umount.c:124
 jfs_put_super+0x8c/0x190 fs/jfs/super.c:194
 generic_shutdown_super+0x13d/0x2d0 fs/super.c:769
 kill_block_super+0x44/0xa0 fs/super.c:1918
 deactivate_locked_super+0xbc/0x110 fs/super.c:603
 cleanup_mnt+0x3d3/0x460 fs/namespace.c:1317
 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:70 [inline]
 exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
 __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:336 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888030829800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 536 bytes inside of
 freed 1024-byte region [ffff888030829800, ffff888030829c00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88803082e800 pfn:0x30828
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 ffff88801b041dc0 ffffea0000a7d410 ffffea0000ac4e10
raw: ffff88803082e800 0000000000100009 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88801b041dc0 ffffea0000a7d410 ffffea0000ac4e10
head: ffff88803082e800 0000000000100009 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 8863, tgid 8863 (kworker/u8:14), ts 301205333734
 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+0x2209/0x2280 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x217/0x5a0 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab+0x7d/0x620 mm/slub.c:3462
 new_slab mm/slub.c:3513 [inline]
 refill_objects+0x2d5/0x350 mm/slub.c:7410
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x2c8/0x6c0 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_noprof+0x47b/0x720 mm/slub.c:5439
 _kmalloc_noprof include/linux/slab.h:995 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 ieee802_11_parse_elems_full+0x14b/0x2de0 net/mac80211/parse.c:1071
 ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2548 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1542 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x509/0x2c40 net/mac80211/ibss.c:1573
 ieee80211_iface_process_skb net/mac80211/iface.c:1769 [inline]
 ieee80211_iface_work+0x78a/0x1010 net/mac80211/iface.c:1823
 cfg80211_wiphy_work+0x29e/0x420 net/wireless/core.c:541
 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/0x480 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
page last free pid 10464 tgid 10464 ts 301151524531 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0xc93/0xd90 mm/page_alloc.c:2962
 __slab_free+0x274/0x2c0 mm/slub.c:5815
 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:4683 [inline]
 slab_alloc_node mm/slub.c:4996 [inline]
 kmem_cache_alloc_noprof+0x2b9/0x600 mm/slub.c:5010
 mt_alloc_one lib/maple_tree.c:139 [inline]
 mas_alloc_nodes+0x291/0x350 lib/maple_tree.c:1089
 mas_preallocate+0x2cf/0x630 lib/maple_tree.c:4961
 vma_iter_prealloc mm/vma.h:636 [inline]
 commit_merge+0x212/0xa70 mm/vma.c:805
 vma_expand+0x81e/0xf40 mm/vma.c:1267
 relocate_vma_down+0x35f/0x560 mm/vma_exec.c:63
 setup_arg_pages+0x6ff/0xbd0 fs/exec.c:695
 load_elf_binary+0xc6c/0x28d0 fs/binfmt_elf.c:1028
 search_binary_handler fs/exec.c:1759 [inline]
 exec_binprm fs/exec.c:1791 [inline]
 bprm_execve+0x930/0x1590 fs/exec.c:1847
 do_execveat_common+0x4f4/0x670 fs/exec.c:1945
 __do_sys_execve fs/exec.c:2018 [inline]
 __se_sys_execve fs/exec.c:2012 [inline]
 __x64_sys_execve+0x97/0xc0 fs/exec.c:2012

Memory state around the buggy address:
 ffff888030829900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888030829980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888030829a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888030829a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888030829b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/25 05:50 upstream 66498c75b4f8 23caa175 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Write in lmLogSync
2026/08/13 03:18 upstream 3d6d817622b0 67796a05 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root KASAN: slab-use-after-free Write in lmLogSync
2026/08/10 15:40 upstream db2ddb871435 039457bd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root KASAN: slab-use-after-free Write in lmLogSync
2026/06/25 19:00 upstream ab9de95c9cf9 432fd51a .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Write in lmLogSync
2026/06/12 19:18 upstream 1dadb7e7eb5a 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Write in lmLogSync
2026/06/09 19:01 upstream 2d3090a8aeb5 c36c07f6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Write in lmLogSync
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
2026/08/20 01:53 upstream e8bf40d15402 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in lmLogSync
* Struck through repros no longer work on HEAD.