KASAN: slab-use-after-free Read in xfs_defer_item_unpause

Status: upstream: reported C repro on 2026/07/31 02:50
Subsystems: xfs
Labels: prio:normal actionable
[Documentation on labels]
Reported-by: syzbot+e7f24354da9f7915bc54@syzkaller.appspotmail.com
First crash: 101d, last: 7d04h
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
2df509ae repro-c 💥 KASAN: slab-use-after-free Read in xfs_defer_item_unpause 2026/10/15 08:12 2026/10/15 08:13 2026/10/15 13:33 8fb0ae89
160540af moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in xfs_defer_item_unpause 2026/07/31 01:57 2026/07/31 01:57 2026/07/31 02:49 aaffb173
9400c1d6 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in xfs_defer_item_unpause 2026/07/27 01:15 2026/07/27 01:15 2026/07/27 01:53 492bab15
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[syzbot] Monthly xfs report (Nov 2026) 0 (1) 2026/11/01 20:33
[syzbot] [xfs?] KASAN: slab-use-after-free Read in xfs_defer_item_unpause 0 (2) 2026/10/18 12:52
[PATCH] xfs: fix slab-use-after-free in xrep_newbt_free() 6 (6) 2026/10/17 04:54
[syzbot] Monthly xfs report (Sep 2026) 0 (1) 2026/09/18 12:33

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in xfs_defer_item_unpause+0x116/0x250 fs/xfs/libxfs/xfs_defer.c:1256
Read of size 4 at addr ffff88803b37d0fc by task syz.0.22/5598

CPU: 0 UID: 0 PID: 5598 Comm: syz.0.22 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
 xfs_defer_item_unpause+0x116/0x250 fs/xfs/libxfs/xfs_defer.c:1256
 xrep_newbt_free+0x3fe/0x5f0 fs/xfs/scrub/newbt.c:522
 xrep_ibt_build_new_trees+0xafd/0xdc0 fs/xfs/scrub/ialloc_repair.c:752
 xrep_iallocbt+0x24e/0x340 fs/xfs/scrub/ialloc_repair.c:828
 xrep_attempt+0x184/0x7c0 fs/xfs/scrub/repair.c:78
 xfs_scrub_metadata+0xce4/0x1910 fs/xfs/scrub/scrub.c:747
 xfs_ioc_scrubv_metadata+0x7ac/0xb70 fs/xfs/scrub/scrub.c:980
 xfs_file_ioctl+0x916/0x1590 fs/xfs/xfs_ioctl.c:1308
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/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
RIP: 0033:0x7fc864b9e559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc865a8b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc864e25fa0 RCX: 00007fc864b9e559
RDX: 0000200000041d40 RSI: 00000000c0285840 RDI: 0000000000000005
RBP: 00007fc864c35ab8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc864e26038 R14: 00007fc864e25fa0 R15: 00007ffe67582028
 </TASK>

Allocated by task 5598:
 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:351 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:377
 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
 xfs_defer_alloc fs/xfs/libxfs/xfs_defer.c:843 [inline]
 xfs_defer_add+0x143/0x480 fs/xfs/libxfs/xfs_defer.c:871
 xfs_extent_free_defer_add+0x1bf/0x3b0 fs/xfs/xfs_extfree_item.c:507
 xfs_defer_extent_free+0x2a8/0x400 fs/xfs/libxfs/xfs_alloc.c:2682
 xfs_alloc_schedule_autoreap+0xb0/0x170 fs/xfs/libxfs/xfs_alloc.c:2727
 xrep_newbt_add_blocks+0x22a/0x3f0 fs/xfs/scrub/newbt.c:211
 xrep_newbt_alloc_ag_blocks+0x81e/0xcc0 fs/xfs/scrub/newbt.c:311
 xrep_ibt_build_new_trees+0x75e/0xdc0 fs/xfs/scrub/ialloc_repair.c:696
 xrep_iallocbt+0x24e/0x340 fs/xfs/scrub/ialloc_repair.c:828
 xrep_attempt+0x184/0x7c0 fs/xfs/scrub/repair.c:78
 xfs_scrub_metadata+0xce4/0x1910 fs/xfs/scrub/scrub.c:747
 xfs_ioc_scrubv_metadata+0x7ac/0xb70 fs/xfs/scrub/scrub.c:980
 xfs_file_ioctl+0x916/0x1590 fs/xfs/xfs_ioctl.c:1308
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/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 5598:
 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:264 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2748 [inline]
 slab_free mm/slub.c:6509 [inline]
 kmem_cache_free+0x182/0x650 mm/slub.c:6636
 xfs_defer_cancel_list fs/xfs/libxfs/xfs_defer.c:505 [inline]
 xfs_defer_finish_noroll+0xf8b/0x14e0 fs/xfs/libxfs/xfs_defer.c:737
 xfs_defer_finish+0x1c/0x180 fs/xfs/libxfs/xfs_defer.c:755
 xrep_defer_finish+0x16e/0x240 fs/xfs/scrub/repair.c:242
 xrep_newbt_alloc_ag_blocks+0x86c/0xcc0 fs/xfs/scrub/newbt.c:318
 xrep_ibt_build_new_trees+0x75e/0xdc0 fs/xfs/scrub/ialloc_repair.c:696
 xrep_iallocbt+0x24e/0x340 fs/xfs/scrub/ialloc_repair.c:828
 xrep_attempt+0x184/0x7c0 fs/xfs/scrub/repair.c:78
 xfs_scrub_metadata+0xce4/0x1910 fs/xfs/scrub/scrub.c:747
 xfs_ioc_scrubv_metadata+0x7ac/0xb70 fs/xfs/scrub/scrub.c:980
 xfs_file_ioctl+0x916/0x1590 fs/xfs/xfs_ioctl.c:1308
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/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 ffff88803b37d0c0
 which belongs to the cache xfs_defer_pending of size 64
The buggy address is located 60 bytes inside of
 freed 64-byte region [ffff88803b37d0c0, ffff88803b37d100)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88803b37d600 pfn:0x3b37d
flags: 0x4fff00000000200(workingset|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000200 ffff888033947dc0 ffff888033c36588 ffff888033c36588
raw: ffff88803b37d600 00000002002a0010 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 131, tgid 131 (kworker/u4:5), ts 153391648879
 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:7418
 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]
 kmem_cache_alloc_noprof+0x399/0x600 mm/slub.c:5010
 xfs_defer_alloc fs/xfs/libxfs/xfs_defer.c:843 [inline]
 xfs_defer_add+0x143/0x480 fs/xfs/libxfs/xfs_defer.c:871
 xfs_bmap_add_extent_hole_real+0xd61/0x1a40 fs/xfs/libxfs/xfs_bmap.c:2782
 xfs_bmapi_allocate+0x248c/0x2f20 fs/xfs/libxfs/xfs_bmap.c:3975
 xfs_bmapi_write+0x843/0x1330 fs/xfs/libxfs/xfs_bmap.c:4265
 xfs_dquot_disk_alloc+0x4af/0xae0 fs/xfs/xfs_dquot.c:385
 xfs_qm_dqread+0xfe/0x520 fs/xfs/xfs_dquot.c:724
 xfs_qm_dqget+0x18a/0x3d0 fs/xfs/xfs_dquot.c:927
 xfs_qm_quotacheck_dqadjust+0xdd/0x5a0 fs/xfs/xfs_qm.c:1260
 xfs_qm_dqusage_adjust+0x4ad/0x670 fs/xfs/xfs_qm.c:1389
page last free pid 9 tgid 9 ts 153295791972 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: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:361
 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+0x29f/0x600 mm/slub.c:5559
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 nsim_fib6_rt_create drivers/net/netdevsim/fib.c:547 [inline]
 nsim_fib6_rt_insert drivers/net/netdevsim/fib.c:752 [inline]
 nsim_fib6_event drivers/net/netdevsim/fib.c:856 [inline]
 nsim_fib_event+0xf37/0xa3a0 drivers/net/netdevsim/fib.c:889
 nsim_fib_event_work+0x244/0x3b0 drivers/net/netdevsim/fib.c:1493
 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/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

Memory state around the buggy address:
 ffff88803b37cf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88803b37d000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88803b37d080: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
                                                                ^
 ffff88803b37d100: fc fc fc fc fa fb fb fb fb fb fb fb fc fc fc fc
 ffff88803b37d180: fa fb fb fb fb fb fb fb fc fc fc fc fa fb fb fb
==================================================================

Crashes (27):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/18 12:51 upstream 32c52ec87d62 432c0077 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/28 11:10 upstream 65ba8f34ec88 858db2ec .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/27 20:33 upstream 62c457528529 96923c60 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/20 17:12 upstream f47d223627f8 df8746fb .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/18 08:20 upstream 32c52ec87d62 432c0077 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/14 09:18 upstream ca3e345926b0 7321cd29 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/07 16:56 upstream 602042bf29f6 6520ecdb .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/07 06:19 upstream 69f80fef3153 f7710056 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/02 03:36 upstream d24e8ac715de 6d32eb1f .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/10/01 18:38 upstream d24e8ac715de 6d32eb1f .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/29 18:52 upstream 6f8319e3e9a4 328436b3 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/25 12:19 upstream 165768bb7026 f281d9d2 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/25 05:53 upstream 5fc5768c7ca9 27d05fb3 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/22 22:50 upstream c4e9f74da438 3e2106e5 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/17 14:20 upstream 238650ef6c7c 4a607247 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/14 04:28 upstream d681d7ef617e 70a60e12 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/04 10:17 upstream 8ab1afb2eb24 801f0966 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/04 10:15 upstream 8ab1afb2eb24 801f0966 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/04 10:09 upstream 8ab1afb2eb24 801f0966 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/04 10:05 upstream 8ab1afb2eb24 801f0966 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/03 16:55 upstream 940de590b839 a8a356ea .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/03 01:53 upstream 940de590b839 6a988719 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/09/01 20:32 upstream bf1079577a11 587f6b29 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/08/28 19:14 upstream 818bebeb63dd 41d151d4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/08/25 03:17 upstream 818bebeb63dd 614e416a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/08/21 02:05 upstream 9d2ed026f031 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
2026/07/26 01:02 upstream 0ce37745d4bf 492bab15 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in xfs_defer_item_unpause
* Struck through repros no longer work on HEAD.