syzbot


KASAN: slab-use-after-free Write in defer_free

Status: fixed on 2026/01/21 09:45
Subsystems: bpf
[Documentation on labels]
Reported-by: syzbot+7a25305a76d872abcfa1@syzkaller.appspotmail.com
Fix commit: 53ca00a19d34 mm/slub: reset KASAN tag in defer_free() before accessing freed memory
First crash: 51d, last: 34d
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] mm/slub: reset KASAN tag in defer_free() before accessing freed memory 3 (3) 2025/12/10 12:58
[syzbot] [bpf?] KASAN: slab-use-after-free Write in defer_free 0 (2) 2025/12/10 01:44
Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/12/10 01:44 28m kartikey406@gmail.com patch upstream OK log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in defer_free+0x3c/0xbc mm/slub.c:6537
Write at addr f3f000000854f020 by task kworker/u8:6/983
Pointer tag: [f3], memory tag: [fe]

CPU: 0 UID: 0 PID: 983 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT 
Hardware name: linux,dummy-virt (DT)
Workqueue: events_unbound bpf_map_free_deferred
Call trace:
 show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x78/0x90 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x108/0x61c mm/kasan/report.c:482
 kasan_report+0x88/0xac mm/kasan/report.c:595
 report_tag_fault arch/arm64/mm/fault.c:330 [inline]
 do_tag_recovery arch/arm64/mm/fault.c:342 [inline]
 __do_kernel_fault+0x170/0x1c8 arch/arm64/mm/fault.c:384
 do_bad_area+0x68/0x78 arch/arm64/mm/fault.c:484
 do_tag_check_fault+0x34/0x44 arch/arm64/mm/fault.c:857
 do_mem_abort+0x44/0x94 arch/arm64/mm/fault.c:933
 el1_abort+0x44/0x68 arch/arm64/kernel/entry-common.c:303
 el1h_64_sync_handler+0x50/0xac arch/arm64/kernel/entry-common.c:437
 el1h_64_sync+0x6c/0x70 arch/arm64/kernel/entry.S:591
 defer_free+0x3c/0xbc mm/slub.c:6537 (P)
 do_slab_free mm/slub.c:6619 [inline]
 kfree_nolock+0x1a0/0x1d4 mm/slub.c:6930
 range_tree_destroy+0x74/0x90 kernel/bpf/range_tree.c:253
 arena_map_free+0x64/0x90 kernel/bpf/arena.c:196
 bpf_map_free kernel/bpf/syscall.c:894 [inline]
 bpf_map_free_deferred+0x70/0x180 kernel/bpf/syscall.c:921
 process_one_work+0x178/0x2cc kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x24c/0x354 kernel/workqueue.c:3421
 kthread+0x130/0x1fc kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

Allocated by task 3570:
 kasan_save_stack+0x3c/0x64 mm/kasan/common.c:56
 save_stack_info+0x40/0x158 mm/kasan/tags.c:106
 kasan_save_alloc_info+0x14/0x20 mm/kasan/tags.c:142
 poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
 poison_kmalloc_redzone mm/kasan/common.c:373 [inline]
 __kasan_kmalloc+0xb4/0xb8 mm/kasan/common.c:417
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 kmalloc_nolock_noprof+0x1dc/0x4fc mm/slub.c:5751
 range_tree_set+0x644/0x778 kernel/bpf/range_tree.c:237
 arena_map_alloc+0x11c/0x17c kernel/bpf/arena.c:141
 map_create+0x19c/0xa98 kernel/bpf/syscall.c:1514
 __sys_bpf+0x348/0x1a88 kernel/bpf/syscall.c:6146
 __do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
 __arm64_sys_bpf+0x24/0x34 kernel/bpf/syscall.c:6272
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x48/0x110 arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x1c/0x28 arch/arm64/kernel/syscall.c:151
 el0_svc+0x34/0x128 arch/arm64/kernel/entry-common.c:724
 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:743
 el0t_64_sync+0x1a4/0x1a8 arch/arm64/kernel/entry.S:596

Freed by task 983:
 kasan_save_stack+0x3c/0x64 mm/kasan/common.c:56
 save_stack_info+0x40/0x158 mm/kasan/tags.c:106
 __kasan_save_free_info+0x18/0x24 mm/kasan/tags.c:147
 kasan_save_free_info mm/kasan/kasan.h:406 [inline]
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x80/0x84 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 kfree_nolock+0xcc/0x1d4 mm/slub.c:6929
 range_tree_destroy+0x74/0x90 kernel/bpf/range_tree.c:253
 arena_map_free+0x64/0x90 kernel/bpf/arena.c:196
 bpf_map_free kernel/bpf/syscall.c:894 [inline]
 bpf_map_free_deferred+0x70/0x180 kernel/bpf/syscall.c:921
 process_one_work+0x178/0x2cc kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x24c/0x354 kernel/workqueue.c:3421
 kthread+0x130/0x1fc kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

The buggy address belongs to the object at fff000000854f000
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 32 bytes inside of
 64-byte region [fff000000854f000, fff000000854f040)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xfbf000000854f200 pfn:0x4854f
flags: 0x1ffc00000000000(node=0|zone=0|lastcpupid=0x7ff|kasantag=0x0)
page_type: f5(slab)
raw: 01ffc00000000000 f9f0000003001600 dead000000000100 dead000000000122
raw: fbf000000854f200 000000008040003f 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 fff000000854ee00: f6 f6 f7 f7 fa fa f9 f9 f5 f5 fb fb f6 f6 fc fc
 fff000000854ef00: f8 f8 f6 f6 f0 f0 f2 f2 f9 f9 f2 f2 f0 f0 fb fb
>fff000000854f000: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
                         ^
 fff000000854f100: fa fa fa fe fe fe fe fe fe fe fe fe fe fe fe fe
 fff000000854f200: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
==================================================================

Crashes (238):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/04 23:56 upstream 559e608c4655 cee4cb10 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/04 22:54 upstream 559e608c4655 cee4cb10 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/21 07:06 upstream d8ba32c5a460 e14dbeb9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/21 04:58 upstream d8ba32c5a460 e14dbeb9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/20 07:44 upstream dd9b004b7ff3 e14dbeb9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/20 01:00 upstream dd9b004b7ff3 e14dbeb9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/19 08:09 upstream 516471569089 e14dbeb9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/19 07:46 upstream 516471569089 e14dbeb9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/18 19:48 upstream ea1013c15392 d6d0fdea .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/18 03:49 upstream ea1013c15392 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/17 14:57 upstream ea1013c15392 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/17 14:54 upstream ea1013c15392 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/16 19:16 upstream 40fbbd64bba6 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/16 18:12 upstream 40fbbd64bba6 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/16 07:24 upstream 8f0b4cce4481 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/15 18:09 upstream 8f0b4cce4481 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/15 16:09 upstream 8f0b4cce4481 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/14 16:11 upstream 8f0b4cce4481 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/14 06:50 upstream 9d9c1cfec01c a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/14 06:45 upstream 9d9c1cfec01c a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/14 02:55 upstream 9d9c1cfec01c a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/13 15:33 upstream 9551a26f17d9 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/13 14:25 upstream 9551a26f17d9 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/13 14:00 upstream 9551a26f17d9 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/12 21:49 upstream 187d0801404f a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/12 20:02 upstream 187d0801404f a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/11 21:19 upstream d358e5254674 a066d2bc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/11 03:50 upstream 0048fbb4011e 48b27acc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/10 14:09 upstream c9b47175e913 48b27acc .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/10 01:27 upstream cb015814f8b6 fc20f974 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/10 01:16 upstream cb015814f8b6 fc20f974 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/09 15:03 upstream cfd4039213e7 fc20f974 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/09 11:55 upstream cfd4039213e7 fc20f974 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/09 10:49 upstream cfd4039213e7 fc20f974 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/09 02:06 upstream c2f2b01b74be fc20f974 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/08 22:13 upstream c2f2b01b74be fc20f974 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/08 21:10 upstream c2f2b01b74be fc20f974 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/08 06:18 upstream 67a454e6b1c6 cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/07 23:18 upstream 67a454e6b1c6 cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/07 16:06 upstream 37bb2e7217b0 cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/07 10:08 upstream 37bb2e7217b0 cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/07 05:08 upstream 416f99c3b16f cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/07 02:11 upstream 416f99c3b16f cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/06 20:23 upstream 416f99c3b16f cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/06 14:00 upstream 3af870aedbff cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/06 06:58 upstream 3af870aedbff cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/06 00:42 upstream 2061f18ad76e cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
2025/12/05 17:24 upstream 2061f18ad76e cee4cb10 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in defer_free
* Struck through repros no longer work on HEAD.