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

Status: premoderation: reported on 2026/08/06 18:51
Reported-by: syzbot+7b13ddb93b8371c58d3c@syzkaller.appspotmail.com
First crash: 1d18h, last: 1d18h

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in msg_word net/tipc/msg.h:207 [inline]
BUG: KASAN: slab-use-after-free in msg_bits net/tipc/msg.h:217 [inline]
BUG: KASAN: slab-use-after-free in msg_dest_droppable net/tipc/msg.h:304 [inline]
BUG: KASAN: slab-use-after-free in tipc_skb_dump+0x132f/0x17e0 net/tipc/trace.c:118
Read of size 4 at addr ffff8881139e3530 by task syz.1.230/978

CPU: 1 UID: 0 PID: 978 Comm: syz.1.230 Not tainted syzkaller #0 67f5df147bfe8fe71cdb2f404f013e40b3f12e05
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 print_address_description+0x71/0x210 mm/kasan/report.c:377
 print_report+0x4a/0x70 mm/kasan/report.c:481
 kasan_report+0x162/0x1a0 mm/kasan/report.c:594
 __asan_report_load4_noabort+0x18/0x20 mm/kasan/report_generic.c:380
 msg_word net/tipc/msg.h:207 [inline]
 msg_bits net/tipc/msg.h:217 [inline]
 msg_dest_droppable net/tipc/msg.h:304 [inline]
 tipc_skb_dump+0x132f/0x17e0 net/tipc/trace.c:118
 tipc_list_dump+0x22f/0x300 net/tipc/trace.c:187
 tipc_sk_dump+0xa16/0xfd0 net/tipc/socket.c:3998
 do_trace_event_raw_event_tipc_sk_class net/tipc/trace.h:205 [inline]
 trace_event_raw_event_tipc_sk_class+0x290/0x4d0 net/tipc/trace.h:188
 trace_tipc_sk_overlimit1 net/tipc/trace.h:241 [inline]
 tipc_sk_enqueue net/tipc/socket.c:2455 [inline]
 tipc_sk_rcv+0x165f/0x2c70 net/tipc/socket.c:2497
 tipc_node_xmit+0x346/0x10e0 net/tipc/node.c:1701
 __tipc_sendmsg+0x1b36/0x28a0 net/tipc/socket.c:1511
 tipc_sendmsg+0x59/0x90 net/tipc/socket.c:1399
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x9a1/0xa00 net/socket.c:2609
 ___sys_sendmsg+0x2a6/0x370 net/socket.c:2663
 __sys_sendmmsg+0x2b4/0x4e0 net/socket.c:2749
 __do_sys_sendmmsg net/socket.c:2778 [inline]
 __se_sys_sendmmsg net/socket.c:2775 [inline]
 __x64_sys_sendmmsg+0xa4/0xc0 net/socket.c:2775
 x64_sys_call+0xfec/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f6a7939e0d9
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:00007f6a7a24e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f6a79625fa0 RCX: 00007f6a7939e0d9
RDX: 00000000040001b6 RSI: 0000200000001540 RDI: 0000000000000009
RBP: 00007f6a79435024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6a79626038 R14: 00007f6a79625fa0 R15: 00007ffffc4d6648
 </TASK>

Allocated by task 978:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_alloc_info+0x3a/0x50 mm/kasan/generic.c:565
 unpoison_slab_object mm/kasan/common.c:321 [inline]
 __kasan_slab_alloc+0x73/0x90 mm/kasan/common.c:347
 kasan_slab_alloc include/linux/kasan.h:251 [inline]
 slab_post_alloc_hook mm/slub.c:4202 [inline]
 slab_alloc_node mm/slub.c:4251 [inline]
 kmem_cache_alloc_node_noprof+0x1ca/0x420 mm/slub.c:4305
 kmalloc_reserve+0xcf/0x4f0 net/core/skbuff.c:596
 __alloc_skb+0x13f/0x360 net/core/skbuff.c:687
 alloc_skb_fclone include/linux/skbuff.h:1413 [inline]
 tipc_buf_acquire net/tipc/msg.c:72 [inline]
 tipc_msg_build+0x160/0xf20 net/tipc/msg.c:402
 __tipc_sendmsg+0x1693/0x28a0 net/tipc/socket.c:1501
 tipc_sendmsg+0x59/0x90 net/tipc/socket.c:1399
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x9a1/0xa00 net/socket.c:2609
 ___sys_sendmsg+0x2a6/0x370 net/socket.c:2663
 __sys_sendmmsg+0x2b4/0x4e0 net/socket.c:2749
 __do_sys_sendmmsg net/socket.c:2778 [inline]
 __se_sys_sendmmsg net/socket.c:2775 [inline]
 __x64_sys_sendmmsg+0xa4/0xc0 net/socket.c:2775
 x64_sys_call+0xfec/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 979:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_free_info+0x44/0x50 mm/kasan/generic.c:579
 poison_slab_object mm/kasan/common.c:249 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:266
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2445 [inline]
 slab_free mm/slub.c:4714 [inline]
 kfree+0x158/0x440 mm/slub.c:4875
 skb_kfree_head net/core/skbuff.c:1081 [inline]
 skb_free_head net/core/skbuff.c:1093 [inline]
 skb_release_data+0x741/0x9a0 net/core/skbuff.c:1120
 skb_release_all net/core/skbuff.c:1185 [inline]
 __kfree_skb+0x62/0x210 net/core/skbuff.c:1199
 sk_skb_reason_drop+0xd8/0x310 net/core/skbuff.c:1237
 kfree_skb_reason include/linux/skbuff.h:1303 [inline]
 kfree_skb include/linux/skbuff.h:1312 [inline]
 tipc_msg_reverse+0x1a8/0x950 net/tipc/msg.c:684
 tipc_sk_respond+0x139/0x430 net/tipc/socket.c:290
 tsk_rej_rx_queue net/tipc/socket.c:311 [inline]
 __tipc_shutdown+0x9b1/0x14e0 net/tipc/socket.c:575
 tipc_release+0xe0/0x1c40 net/tipc/socket.c:640
 __sock_release net/socket.c:659 [inline]
 sock_close+0xb7/0x220 net/socket.c:1426
 __fput+0x208/0xa30 fs/file_table.c:447
 ____fput+0x20/0x30 fs/file_table.c:475
 task_work_run+0x1e8/0x260 kernel/task_work.c:246
 resume_user_mode_work+0x35/0x50 include/linux/resume_user_mode.h:50
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x63/0xb0 kernel/entry/common.c:218
 do_syscall_64+0x63/0xf0 arch/x86/entry/common.c:84
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The buggy address belongs to the object at ffff8881139e3480
 which belongs to the cache skbuff_small_head of size 768
The buggy address is located 176 bytes inside of
 freed 768-byte region [ffff8881139e3480, ffff8881139e3780)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1139e0
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0x4000000000000040(head|zone=1)
page_type: f5(slab)
raw: 4000000000000040 ffff888101a4b140 ffffea0004569a00 dead000000000005
raw: 0000000000000000 0000000000120012 00000001f5000000 0000000000000000
head: 4000000000000040 ffff888101a4b140 ffffea0004569a00 dead000000000005
head: 0000000000000000 0000000000120012 00000001f5000000 0000000000000000
head: 4000000000000002 ffffea00044e7801 ffffffffffffffff 0000000000000000
head: 0000000000000004 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 111, tgid 111 (udevadm), ts 6587740755, free_ts 0
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook+0x37d/0x3b0 mm/page_alloc.c:1863
 prep_new_page+0x2d/0x180 mm/page_alloc.c:1871
 get_page_from_freelist+0x4aea/0x4ba0 mm/page_alloc.c:3948
 __alloc_pages_noprof+0x35a/0x7e0 mm/page_alloc.c:5315
 alloc_slab_page+0x6b/0x1e0 mm/slub.c:-1
 allocate_slab+0x69/0x430 mm/slub.c:2687
 new_slab mm/slub.c:2741 [inline]
 ___slab_alloc+0x591/0x8c0 mm/slub.c:3934
 __slab_alloc mm/slub.c:4025 [inline]
 __slab_alloc_node mm/slub.c:4078 [inline]
 slab_alloc_node mm/slub.c:4239 [inline]
 kmem_cache_alloc_node_noprof+0x29b/0x420 mm/slub.c:4305
 kmalloc_reserve+0xcf/0x4f0 net/core/skbuff.c:596
 __alloc_skb+0x13f/0x360 net/core/skbuff.c:687
 alloc_skb include/linux/skbuff.h:1363 [inline]
 alloc_uevent_skb+0x85/0x240 lib/kobject_uevent.c:289
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast+0x356/0x5e0 lib/kobject_uevent.c:410
 kobject_uevent_env+0x551/0x7e0 lib/kobject_uevent.c:608
 kobject_synth_uevent+0x417/0xa00 lib/kobject_uevent.c:207
 store_uevent+0x1a/0x30 kernel/module/main.c:963
 module_attr_store+0x74/0xa0 kernel/params.c:910
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881139e3400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881139e3480: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881139e3500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff8881139e3580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881139e3600: fb fb fb fb fb fb fb 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
2026/08/06 18:50 android16-6.12 749a6f9d41aa c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in tipc_skb_dump
* Struck through repros no longer work on HEAD.