KASAN: slab-use-after-free Write in xlog_cil_committed (2)

Status: upstream: reported on 2026/09/30 04:50
Subsystems: xfs
Labels: prio:high actionable
[Documentation on labels]
Reported-by: syzbot+9d8e687768d0f38c1f09@syzkaller.appspotmail.com
First crash: 4d11h, last: 4d11h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
775742a2 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Write in xlog_cil_committed (2) 2026/09/30 03:51 2026/09/30 03:51 2026/09/30 04:49 69537153
431140d7 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Write in xlog_cil_committed (2) 2026/09/27 00:36 2026/09/27 00:36 2026/09/27 01:44 a3c7249d
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [xfs?] KASAN: slab-use-after-free Write in xlog_cil_committed (2) 0 (1) 2026/09/30 04:50
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Write in xlog_cil_committed prio:high xfs 22 syz, C done error 13 138d 404d 0/29 auto-obsoleted due to no activity on 2026/08/23 02:21
linux-5.15 KASAN: use-after-free Read in xlog_cil_committed 19 syz 19 1189d 1288d 0/3 auto-obsoleted due to no activity on 2023/09/12 13:46

Sample crash report:
=========================
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_write include/linux/instrumented.h:97 [inline]
BUG: KASAN: slab-use-after-free in set_bit include/asm-generic/bitops/instrumented-atomic.h:28 [inline]
BUG: KASAN: slab-use-after-free in xlog_cil_ail_insert fs/xfs/xfs_log_cil.c:889 [inline]
BUG: KASAN: slab-use-after-free in xlog_cil_committed+0x4ac/0x1110 fs/xfs/xfs_log_cil.c:995
Write of size 8 at addr ffff88803c610820 by task kworker/u8:5/69

CPU: 1 UID: 0 PID: 69 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: xfs-cil/loop4 xlog_cil_push_work
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
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
 instrument_atomic_write include/linux/instrumented.h:97 [inline]
 set_bit include/asm-generic/bitops/instrumented-atomic.h:28 [inline]
 xlog_cil_ail_insert fs/xfs/xfs_log_cil.c:889 [inline]
 xlog_cil_committed+0x4ac/0x1110 fs/xfs/xfs_log_cil.c:995
 xlog_cil_push_work+0x24b6/0x2a90 fs/xfs/xfs_log_cil.c:1608
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/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 6374:
 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:4683 [inline]
 slab_alloc_node mm/slub.c:4996 [inline]
 kmem_cache_alloc_noprof+0x360/0x690 mm/slub.c:5010
 xfs_buf_item_init+0x6a/0x6e0 fs/xfs/xfs_buf_item.c:872
 _xfs_trans_bjoin+0x46/0x110 fs/xfs/xfs_trans_buf.c:75
 __xfs_trans_getsb+0x65/0x4a0 fs/xfs/xfs_trans_buf.c:191
 xfs_log_sb+0x43/0x200 fs/xfs/libxfs/xfs_sb.c:1327
 xfs_sync_sb_buf+0xc2/0x290 fs/xfs/libxfs/xfs_sb.c:1479
 xfs_ioc_setlabel+0x1d7/0x340 fs/xfs/xfs_ioctl.c:1081
 xfs_file_ioctl+0x901/0x1590 fs/xfs/xfs_ioctl.c:1238
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
 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 6374:
 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:6508 [inline]
 kmem_cache_free+0x187/0x6d0 mm/slub.c:6635
 xfs_buf_ioend+0x235/0x790 fs/xfs/xfs_buf.c:1167
 xfs_buf_iowait+0x133/0x420 fs/xfs/xfs_buf.c:1336
 xfs_bwrite+0x5f/0xe0 fs/xfs/xfs_buf.c:1239
 xfs_sync_sb_buf+0x172/0x290 fs/xfs/libxfs/xfs_sb.c:1489
 xfs_ioc_setlabel+0x1d7/0x340 fs/xfs/xfs_ioctl.c:1081
 xfs_file_ioctl+0x901/0x1590 fs/xfs/xfs_ioctl.c:1238
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
 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

The buggy address belongs to the object at ffff88803c6107e0
 which belongs to the cache xfs_buf_item of size 272
The buggy address is located 64 bytes inside of
 freed 272-byte region [ffff88803c6107e0, ffff88803c6108f0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3c610
flags: 0x80000000000000(node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000000 ffff88801f3d6c80 dead000000000100 dead000000000122
raw: 0000000000000000 00000002000c000c 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 0xd2c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5857, tgid 5854 (syz.4.12), ts 99901674002
 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+0x2591/0x2600 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x230/0x5c0 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+0x2d8/0x350 mm/slub.c:7417
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x339/0x690 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 kmem_cache_alloc_noprof+0x45d/0x690 mm/slub.c:5010
 xfs_buf_item_init+0x6a/0x6e0 fs/xfs/xfs_buf_item.c:872
 _xfs_trans_bjoin+0x46/0x110 fs/xfs/xfs_trans_buf.c:75
 xfs_trans_read_buf_map+0x2ee/0x820 fs/xfs/xfs_trans_buf.c:294
 xfs_trans_read_buf fs/xfs/xfs_trans.h:212 [inline]
 xfs_read_icluster+0x218/0x3e0 fs/xfs/libxfs/xfs_inode_buf.c:139
 xfs_iget_cache_miss fs/xfs/xfs_icache.c:663 [inline]
 xfs_iget+0xc34/0x2f00 fs/xfs/xfs_icache.c:804
 xfs_trans_metafile_iget+0x77/0x330 fs/xfs/xfs_icache.c:853
 xfs_rtginode_load+0x3a3/0x920 fs/xfs/libxfs/xfs_rtgroup.c:469
 xfs_rtmount_rtg fs/xfs/xfs_rtalloc.c:1684 [inline]
 xfs_rtmount_inodes+0x14f/0x7a0 fs/xfs/xfs_rtalloc.c:1721
 xfs_mountfs+0x1254/0x2380 fs/xfs/xfs_mount.c:1095
page last free pid 41 tgid 41 ts 94068259020 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0xf8e/0x1070 mm/page_alloc.c:2962
 __slab_free+0x250/0x2a0 mm/slub.c:5823
 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]
 __kmalloc_cache_noprof+0x353/0x680 mm/slub.c:5559
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 mca_alloc net/ipv6/mcast.c:890 [inline]
 __ipv6_dev_mc_inc+0x447/0xaf0 net/ipv6/mcast.c:981
 addrconf_join_solict net/ipv6/addrconf.c:2262 [inline]
 addrconf_dad_begin net/ipv6/addrconf.c:4135 [inline]
 addrconf_dad_work+0x5dd/0x16e0 net/ipv6/addrconf.c:4263
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/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

Memory state around the buggy address:
 ffff88803c610700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803c610780: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
>ffff88803c610800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff88803c610880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff88803c610900: fc fc fc fc fc fc fa 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
2026/09/25 23:21 upstream aa98230e410f f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Write in xlog_cil_committed
* Struck through repros no longer work on HEAD.