syzbot


KASAN: slab-use-after-free Read in txUnlock (3)

Status: upstream: reported on 2026/07/20 01:38
Subsystems: jfs
Labels: prio:high actionable
[Documentation on labels]
Reported-by: syzbot+8e638a3726a11c61829e@syzkaller.appspotmail.com
First crash: 7d07h, last: 5d02h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
ed804d73-b56e-4f79-bdb5-153eb5dd04b3 moderation Actionable: ✅ KASAN: slab-use-after-free Read in txUnlock (3) 2026/07/20 00:22 2026/07/20 00:22 2026/07/20 01:37 72524a6625c995608a7d179201dff2195b8d1f66

			
		
8a4f440a-036f-4f86-8a70-d4ced2f859ec assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ KASAN: slab-use-after-free Read in txUnlock (3) 2026/07/17 00:57 2026/07/17 00:57 2026/07/17 01:46 49f47391518e9cfe0cedbef0d8259b0041150b4f

			
		
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [jfs?] KASAN: slab-use-after-free Read in txUnlock (3) 0 (1) 2026/07/20 01:38
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in txUnlock jfs 19 1 422d 418d 0/29 auto-obsoleted due to no activity on 2025/08/24 00:02
upstream KASAN: slab-use-after-free Read in txUnlock (2) jfs prio:high 19 1 151d 147d 0/29 auto-obsoleted due to no activity on 2026/05/22 02:39

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in txUnlock+0x951/0xde0 fs/jfs/jfs_txnmgr.c:927
Read of size 2 at addr ffff888031a86c98 by task jfsCommit/108

CPU: 0 UID: 0 PID: 108 Comm: jfsCommit Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
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
 txUnlock+0x951/0xde0 fs/jfs/jfs_txnmgr.c:927
 txLazyCommit fs/jfs/jfs_txnmgr.c:2684 [inline]
 jfs_lazycommit+0x59f/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 5328:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 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
 mempool_alloc_noprof+0x1bf/0x300 mm/mempool.c:559
 alloc_metapage fs/jfs/jfs_metapage.c:264 [inline]
 __get_metapage+0x4ed/0xdf0 fs/jfs/jfs_metapage.c:761
 diWrite+0x401/0x1f60 fs/jfs/jfs_imap.c:639
 txCommit+0x83a/0x54a0 fs/jfs/jfs_txnmgr.c:1257
 __jfs_xattr_set+0x10e/0x170 fs/jfs/xattr.c:943
 __vfs_setxattr+0x442/0x480 fs/xattr.c:223
 __vfs_setxattr_noperm+0x12a/0x660 fs/xattr.c:257
 vfs_setxattr+0x163/0x360 fs/xattr.c:344
 do_setxattr fs/xattr.c:662 [inline]
 filename_setxattr+0x296/0x630 fs/xattr.c:690
 path_setxattrat+0x408/0x450 fs/xattr.c:734
 __do_sys_setxattr fs/xattr.c:768 [inline]
 __se_sys_setxattr fs/xattr.c:764 [inline]
 __x64_sys_setxattr+0xbc/0xe0 fs/xattr.c:764
 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 75:
 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]
 kmem_cache_free+0x182/0x650 mm/slub.c:6532
 mempool_free+0xec/0x130 mm/mempool.c:704
 free_metapage fs/jfs/jfs_metapage.c:280 [inline]
 metapage_release_folio+0x462/0x590 fs/jfs/jfs_metapage.c:637
 shrink_folio_list+0x2364/0x5330 mm/vmscan.c:1463
 evict_folios+0x3821/0x4b40 mm/vmscan.c:4835
 try_to_shrink_lruvec+0xb4f/0xed0 mm/vmscan.c:4983
 shrink_one+0x233/0x730 mm/vmscan.c:5024
 shrink_many mm/vmscan.c:5087 [inline]
 lru_gen_shrink_node mm/vmscan.c:5165 [inline]
 shrink_node+0x3303/0x3b60 mm/vmscan.c:6154
 kswapd_shrink_node mm/vmscan.c:7008 [inline]
 balance_pgdat mm/vmscan.c:7186 [inline]
 kswapd+0x17b6/0x31c0 mm/vmscan.c:7462
 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

The buggy address belongs to the object at ffff888031a86c98
 which belongs to the cache jfs_mp of size 184
The buggy address is located 0 bytes inside of
 freed 184-byte region [ffff888031a86c98, ffff888031a86d50)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x31a86
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000000 ffff8880316b6dc0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 9012459893, free_ts 0
 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]
 kmem_cache_alloc_noprof+0x382/0x5f0 mm/slub.c:4959
 mempool_init_node+0x1f4/0x4f0 mm/mempool.c:259
 mempool_create_node_noprof+0xb8/0x150 mm/mempool.c:323
 metapage_init+0xed/0x150 fs/jfs/jfs_metapage.c:293
 init_jfs_fs+0xfd/0x4e0 fs/jfs/super.c:969
 do_one_initcall+0x250/0x870 init/main.c:1347
 do_initcall_level+0x10a/0x1a0 init/main.c:1409
 do_initcalls+0x59/0xa0 init/main.c:1425
 kernel_init_freeable+0x29d/0x3e0 init/main.c:1658
 kernel_init+0x1d/0x1d0 init/main.c:1548
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888031a86b80: fc fc fc fc fa fb fb fb fb fb fb fb fb fb fb fb
 ffff888031a86c00: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc
>ffff888031a86c80: fc fc fc fa fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888031a86d00: fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc
 ffff888031a86d80: fc fc fa 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
2026/07/17 11:45 upstream fce2dfa773ce 7f27c57a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in txUnlock
2026/07/15 23:51 upstream 58717b2a1365 27a8bd60 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in txUnlock
2026/07/15 06:58 upstream 58717b2a1365 2130f682 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in txUnlock
* Struck through repros no longer work on HEAD.