==================================================================
BUG: KASAN: slab-use-after-free in __lock_acquire+0x2de0/0x3cb0 kernel/locking/lockdep.c:5007
Read of size 8 at addr ffff888026b6c418 by task kworker/u32:8/1106

CPU: 0 UID: 0 PID: 1106 Comm: kworker/u32:8 Not tainted 6.11.0-rc5-syzkaller-00015-g3e9bff3bbe13 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: bat_events batadv_nc_worker
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0xc3/0x620 mm/kasan/report.c:488
 kasan_report+0xd9/0x110 mm/kasan/report.c:601
 __lock_acquire+0x2de0/0x3cb0 kernel/locking/lockdep.c:5007
 lock_acquire kernel/locking/lockdep.c:5759 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
 p9_tag_remove net/9p/client.c:397 [inline]
 p9_req_put net/9p/client.c:405 [inline]
 p9_req_put+0xaf/0x250 net/9p/client.c:402
 req_done+0x1e7/0x2f0 net/9p/trans_virtio.c:147
 vring_interrupt drivers/virtio/virtio_ring.c:2595 [inline]
 vring_interrupt+0x31b/0x400 drivers/virtio/virtio_ring.c:2570
 __handle_irq_event_percpu+0x229/0x7c0 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
 handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:210
 handle_edge_irq+0x263/0xd10 kernel/irq/chip.c:831
 generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
 handle_irq arch/x86/kernel/irq.c:247 [inline]
 call_irq_handler arch/x86/kernel/irq.c:259 [inline]
 __common_interrupt+0xdf/0x250 arch/x86/kernel/irq.c:285
 common_interrupt+0xab/0xd0 arch/x86/kernel/irq.c:278
 </IRQ>
 <TASK>
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
RIP: 0010:lockdep_enabled kernel/locking/lockdep.c:121 [inline]
RIP: 0010:lock_release+0x129/0x6f0 kernel/locking/lockdep.c:5772
Code: 0f 85 d6 02 00 00 65 4c 8b 35 43 97 9a 7e 49 8d be dc 0a 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 <48> 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 59 05 00 00 41
RSP: 0018:ffffc90006bf7ad0 EFLAGS: 00000a03
RAX: dffffc0000000000 RBX: 1ffff92000d7ef5c RCX: ffffffff81694359
RDX: 0000000000000000 RSI: ffffffff8bb05960 RDI: ffff8880205caf1c
RBP: ffffffff901178b8 R08: 0000000000000000 R09: fffffbfff20228fb
R10: ffffffff901147df R11: 0000000000000000 R12: ffffffff8ddb94a0
R13: ffff8880158b0000 R14: ffff8880205ca440 R15: dffffc0000000000
 rcu_lock_release include/linux/rcupdate.h:336 [inline]
 rcu_read_unlock include/linux/rcupdate.h:869 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:412 [inline]
 batadv_nc_worker+0x88c/0x1060 net/batman-adv/network-coding.c:719
 process_one_work+0x958/0x1ad0 kernel/workqueue.c:3231
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xed0 kernel/workqueue.c:3389
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Allocated by task 8071:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:387
 kmalloc_noprof include/linux/slab.h:681 [inline]
 p9_client_create+0xcf/0x11b0 net/9p/client.c:983
 v9fs_session_init+0x1f8/0x1a80 fs/9p/v9fs.c:410
 v9fs_mount+0xc6/0xa50 fs/9p/vfs_super.c:122
 legacy_get_tree+0x109/0x220 fs/fs_context.c:662
 vfs_get_tree+0x8f/0x380 fs/super.c:1800
 do_new_mount fs/namespace.c:3472 [inline]
 path_mount+0x6e1/0x1f10 fs/namespace.c:3799
 do_mount fs/namespace.c:3812 [inline]
 __do_sys_mount fs/namespace.c:4020 [inline]
 __se_sys_mount fs/namespace.c:3997 [inline]
 __ia32_sys_mount+0x292/0x310 fs/namespace.c:3997
 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
 __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Freed by task 8071:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:579
 poison_slab_object+0xf7/0x160 mm/kasan/common.c:240
 __kasan_slab_free+0x32/0x50 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2252 [inline]
 slab_free mm/slub.c:4473 [inline]
 kfree+0x12a/0x3b0 mm/slub.c:4594
 p9_client_create+0x9ca/0x11b0 net/9p/client.c:1054
 v9fs_session_init+0x1f8/0x1a80 fs/9p/v9fs.c:410
 v9fs_mount+0xc6/0xa50 fs/9p/vfs_super.c:122
 legacy_get_tree+0x109/0x220 fs/fs_context.c:662
 vfs_get_tree+0x8f/0x380 fs/super.c:1800
 do_new_mount fs/namespace.c:3472 [inline]
 path_mount+0x6e1/0x1f10 fs/namespace.c:3799
 do_mount fs/namespace.c:3812 [inline]
 __do_sys_mount fs/namespace.c:4020 [inline]
 __se_sys_mount fs/namespace.c:3997 [inline]
 __ia32_sys_mount+0x292/0x310 fs/namespace.c:3997
 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
 __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

The buggy address belongs to the object at ffff888026b6c400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
 freed 512-byte region [ffff888026b6c400, ffff888026b6c600)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888026b6dc00 pfn:0x26b6c
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xfdffffff(slab)
raw: 00fff00000000040 ffff888015842c80 ffffea000048e200 dead000000000002
raw: ffff888026b6dc00 000000008010000e 00000001fdffffff 0000000000000000
head: 00fff00000000040 ffff888015842c80 ffffea000048e200 dead000000000002
head: ffff888026b6dc00 000000008010000e 00000001fdffffff 0000000000000000
head: 00fff00000000002 ffffea00009adb01 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 0x352800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL|__GFP_THISNODE), pid 5840, tgid 5840 (syz-executor), ts 82588410229, free_ts 82564170314
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1493
 prep_new_page mm/page_alloc.c:1501 [inline]
 get_page_from_freelist+0x1351/0x2e50 mm/page_alloc.c:3439
 __alloc_pages_noprof+0x22b/0x2460 mm/page_alloc.c:4695
 __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
 alloc_slab_page+0x4e/0xf0 mm/slub.c:2321
 allocate_slab mm/slub.c:2484 [inline]
 new_slab+0x84/0x260 mm/slub.c:2537
 ___slab_alloc+0xdac/0x1870 mm/slub.c:3723
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3813
 __slab_alloc_node mm/slub.c:3866 [inline]
 slab_alloc_node mm/slub.c:4025 [inline]
 __do_kmalloc_node mm/slub.c:4157 [inline]
 __kmalloc_node_noprof+0x367/0x440 mm/slub.c:4164
 kmalloc_array_node_noprof include/linux/slab.h:788 [inline]
 alloc_slab_obj_exts+0x41/0xa0 mm/slub.c:1976
 account_slab mm/slub.c:2447 [inline]
 allocate_slab mm/slub.c:2502 [inline]
 new_slab+0x20f/0x260 mm/slub.c:2537
 ___slab_alloc+0xdac/0x1870 mm/slub.c:3723
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3813
 __slab_alloc_node mm/slub.c:3866 [inline]
 slab_alloc_node mm/slub.c:4025 [inline]
 kmem_cache_alloc_noprof+0x2ae/0x2f0 mm/slub.c:4044
 leaf_new net/ipv4/fib_trie.c:359 [inline]
 fib_insert_node net/ipv4/fib_trie.c:1115 [inline]
 fib_insert_alias+0x43c/0xe30 net/ipv4/fib_trie.c:1165
 fib_table_insert+0xaab/0x1d70 net/ipv4/fib_trie.c:1379
 fib_magic+0x4d6/0x5c0 net/ipv4/fib_frontend.c:1104
page last free pid 5875 tgid 5875 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1094 [inline]
 free_unref_page+0x64a/0xe40 mm/page_alloc.c:2612
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4e/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x192/0x1e0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:322
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3988 [inline]
 slab_alloc_node mm/slub.c:4037 [inline]
 kmem_cache_alloc_node_noprof+0x153/0x310 mm/slub.c:4080
 __alloc_skb+0x2b3/0x380 net/core/skbuff.c:664
 alloc_skb include/linux/skbuff.h:1320 [inline]
 alloc_skb_with_frags+0xe4/0x710 net/core/skbuff.c:6526
 sock_alloc_send_pskb+0x7f1/0x980 net/core/sock.c:2815
 sock_alloc_send_skb include/net/sock.h:1778 [inline]
 mld_newpack.isra.0+0x1d4/0x7e0 net/ipv6/mcast.c:1746
 add_grhead+0x299/0x340 net/ipv6/mcast.c:1849
 add_grec+0x111e/0x1670 net/ipv6/mcast.c:1987
 mld_send_cr net/ipv6/mcast.c:2113 [inline]
 mld_ifc_work+0x41f/0xca0 net/ipv6/mcast.c:2650
 process_one_work+0x958/0x1ad0 kernel/workqueue.c:3231
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xed0 kernel/workqueue.c:3389
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147

Memory state around the buggy address:
 ffff888026b6c300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888026b6c380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888026b6c400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888026b6c480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888026b6c500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
----------------
Code disassembly (best guess):
   0:	0f 85 d6 02 00 00    	jne    0x2dc
   6:	65 4c 8b 35 43 97 9a 	mov    %gs:0x7e9a9743(%rip),%r14        # 0x7e9a9751
   d:	7e
   e:	49 8d be dc 0a 00 00 	lea    0xadc(%r14),%rdi
  15:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  1c:	fc ff df
  1f:	48 89 fa             	mov    %rdi,%rdx
  22:	48 c1 ea 03          	shr    $0x3,%rdx
  26:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx
* 2a:	48 89 f8             	mov    %rdi,%rax <-- trapping instruction
  2d:	83 e0 07             	and    $0x7,%eax
  30:	83 c0 03             	add    $0x3,%eax
  33:	38 d0                	cmp    %dl,%al
  35:	7c 08                	jl     0x3f
  37:	84 d2                	test   %dl,%dl
  39:	0f 85 59 05 00 00    	jne    0x598
  3f:	41                   	rex.B