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: 69d, last: 7d04h
Cause bisection: failed (error log, bisect log)
  
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
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 76d 1402d 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 232 3d13h 406d 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 1181 5h26m 1237d 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 643 4d23h 1237d 0/3 upstream: reported C repro on 2023/03/14 00:56
upstream general protection fault in lmLogSync jfs 2 1 1576d 1565d 0/29 auto-closed as invalid on 2022/08/06 08:08
Last patch testing requests (1)
Created Duration User Patch Repo Result
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 ffff888078b39a18 by task jfsCommit/119

CPU: 1 UID: 0 PID: 119 Comm: jfsCommit Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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+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 6176:
 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+0x32d/0x660 mm/slub.c:5515
 _kmalloc_noprof include/linux/slab.h:969 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [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:1634
 vfs_get_tree+0x92/0x2a0 fs/super.c:1694
 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 5770:
 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:2705 [inline]
 slab_free mm/slub.c:6405 [inline]
 kfree+0x1c5/0x640 mm/slub.c:6720
 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:647
 kill_block_super+0x44/0x90 fs/super.c:1665
 deactivate_locked_super+0xbc/0x130 fs/super.c:477
 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+0x1fa/0x730 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:318 [inline]
 do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888078b39800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 536 bytes inside of
 freed 1024-byte region [ffff888078b39800, ffff888078b39c00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x78b38
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813fe25dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe25dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 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 6055, tgid 6055 (kworker/u8:2), ts 107606662230, free_ts 107579789139
 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+0x21fa/0x2270 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3294 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3408
 new_slab mm/slub.c:3454 [inline]
 refill_objects+0x2d5/0x350 mm/slub.c:7338
 refill_sheaf mm/slub.c:2832 [inline]
 __pcs_replace_empty_main+0x2bf/0x6b0 mm/slub.c:4703
 alloc_from_pcs mm/slub.c:4801 [inline]
 slab_alloc_node mm/slub.c:4933 [inline]
 __do_kmalloc_node mm/slub.c:5361 [inline]
 __kmalloc_noprof+0x485/0x720 mm/slub.c:5387
 _kmalloc_noprof include/linux/slab.h:973 [inline]
 load_elf_phdrs fs/binfmt_elf.c:540 [inline]
 load_elf_binary+0x2c3/0x2950 fs/binfmt_elf.c:869
 search_binary_handler fs/exec.c:1694 [inline]
 exec_binprm fs/exec.c:1726 [inline]
 bprm_execve+0x9c7/0x1630 fs/exec.c:1778
 kernel_execve+0x8c3/0x9c0 fs/exec.c:1922
 call_usermodehelper_exec_async+0x20f/0x360 kernel/umh.c:109
 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 4986 tgid 4986 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0xc1e/0xd10 mm/page_alloc.c:2950
 __slab_free+0x274/0x2c0 mm/slub.c:5767
 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:4612 [inline]
 slab_alloc_node mm/slub.c:4945 [inline]
 kmem_cache_alloc_noprof+0x2a0/0x5f0 mm/slub.c:4959
 alloc_filename fs/namei.c:147 [inline]
 do_getname+0x2e/0x250 fs/namei.c:187
 class_filename_flags_constructor include/linux/fs.h:2561 [inline]
 do_readlinkat+0xc8/0x510 fs/stat.c:569
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x7f/0x90 fs/stat.c:602
 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

Memory state around the buggy address:
 ffff888078b39900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888078b39980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888078b39a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888078b39a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888078b39b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
* Struck through repros no longer work on HEAD.