syzbot

 sign-in | mailing list | source | docs | 🏰
🐞 Open [1328]
≡ Subsystems
🐞 Fixed [7155]
🐞 Invalid [18915]
⬇ Missing Backports [220]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
Total Repo Heatmap Subsystems Heatmap
✨ AI
💬 Send us feedback

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: 19d, last: 13h47m
▶ ▼ ✨ 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 (2)
Title Replies (including bot) Last reply
[PATCH] jfs: fix use-after-free in lmLogSync during unmount 1 (1) 2026/06/03 17:16
[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 26d 1352d 29/29 fixed on 2026/05/21 07:49
linux-6.6 general protection fault in lmLogSync origin:upstream missing-backport 22 C error 212 56m 356d 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 1141 4h09m 1187d 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 15d 1187d 0/3 upstream: reported C repro on 2023/03/14 00:56
upstream general protection fault in lmLogSync jfs 2 1 1527d 1515d 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+0x9a5/0xa40 fs/jfs/jfs_logmgr.c:1003
Write of size 4 at addr ffff88807f47ba18 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 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+0x389/0x470 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 25473:
 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+0x318/0x660 mm/slub.c:5420
 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+0x2d1/0xf90 fs/jfs/jfs_logmgr.c:1067
 jfs_mount_rw+0xf3/0x670 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0x772/0xd90 fs/jfs/super.c:532
 get_tree_bdev_flags+0x430/0x4f0 fs/super.c:1694
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3761 [inline]
 do_new_mount+0x319/0xdc0 fs/namespace.c:3837
 do_mount fs/namespace.c:4170 [inline]
 __do_sys_mount fs/namespace.c:4386 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4363
 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 23089:
 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:2689 [inline]
 slab_free mm/slub.c:6251 [inline]
 kfree+0x1c5/0x640 mm/slub.c:6566
 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:646
 kill_block_super+0x44/0x90 fs/super.c:1725
 deactivate_locked_super+0xbc/0x130 fs/super.c:476
 cleanup_mnt+0x3d3/0x460 fs/namespace.c:1312
 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:67 [inline]
 exit_to_user_mode_loop+0x193/0x6b0 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+0x353/0x580 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807f47b800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 536 bytes inside of
 freed 1024-byte region [ffff88807f47b800, ffff88807f47bc00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7f478
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 ffff88813fe18dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe18dc0 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5628, tgid 5628 (syz-executor), ts 86721145205, free_ts 86710149016
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x24ae/0x2530 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3467
 new_slab mm/slub.c:3525 [inline]
 refill_objects+0x336/0x3d0 mm/slub.c:7272
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x320/0x720 mm/slub.c:4652
 alloc_from_pcs mm/slub.c:4750 [inline]
 slab_alloc_node mm/slub.c:4884 [inline]
 __kmalloc_cache_noprof+0x388/0x660 mm/slub.c:5415
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 batadv_hardif_add_interface net/batman-adv/hard-interface.c:874 [inline]
 batadv_hard_if_event+0xe64/0x16b0 net/batman-adv/hard-interface.c:958
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
 call_netdevice_notifiers net/core/dev.c:2301 [inline]
 register_netdevice+0x18db/0x1f00 net/core/dev.c:11461
 veth_newlink+0x676/0xb70 drivers/net/veth.c:1890
 rtnl_newlink_create+0x310/0xb00 net/core/rtnetlink.c:3864
 __rtnl_newlink net/core/rtnetlink.c:3995 [inline]
 rtnl_newlink+0x167f/0x1bd0 net/core/rtnetlink.c:4110
 rtnetlink_rcv_msg+0x802/0xc00 net/core/rtnetlink.c:6997
 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2555
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x7bb/0x940 net/netlink/af_netlink.c:1344
page last free pid 5639 tgid 5639 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1397 [inline]
 __free_frozen_pages+0xc0d/0xd20 mm/page_alloc.c:2938
 __slab_free+0x274/0x2c0 mm/slub.c:5613
 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:4570 [inline]
 slab_alloc_node mm/slub.c:4899 [inline]
 __do_kmalloc_node mm/slub.c:5295 [inline]
 __kmalloc_noprof+0x312/0x750 mm/slub.c:5308
 kmalloc_noprof include/linux/slab.h:954 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 ethnl_default_notify+0x1ab/0xbf0 net/ethtool/netlink.c:989
 ethtool_notify net/ethtool/netlink.c:1094 [inline]
 ethnl_notify_features net/ethtool/netlink.c:1102 [inline]
 ethnl_netdev_event+0xe2/0x160 net/ethtool/netlink.c:1117
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
 call_netdevice_notifiers net/core/dev.c:2301 [inline]
 netdev_features_change net/core/dev.c:1590 [inline]
 netdev_change_features net/core/dev.c:11103 [inline]
 netdev_compute_master_upper_features+0x944/0xb30 net/core/dev.c:12870
 br_add_if+0xc16/0xea0 net/bridge/br_if.c:683
 do_set_master+0x563/0x720 net/core/rtnetlink.c:2986
 do_setlink+0xe7b/0x4670 net/core/rtnetlink.c:3188
 rtnl_changelink net/core/rtnetlink.c:3800 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3973 [inline]
 rtnl_newlink+0x15c2/0x1bd0 net/core/rtnetlink.c:4110
 rtnetlink_rcv_msg+0x802/0xc00 net/core/rtnetlink.c:6997
 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2555

Memory state around the buggy address:
 ffff88807f47b900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807f47b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807f47ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88807f47ba80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807f47bb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.