==================================================================
BUG: KASAN: slab-use-after-free in __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
BUG: KASAN: slab-use-after-free in _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
Read of size 1 at addr ffff88805500e818 by task syz.9.6087/27674

CPU: 3 UID: 0 PID: 27674 Comm: syz.9.6087 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xcd/0x630 mm/kasan/report.c:482
 kasan_report+0xe0/0x110 mm/kasan/report.c:595
 __kasan_check_byte+0x36/0x50 mm/kasan/common.c:574
 kasan_check_byte include/linux/kasan.h:402 [inline]
 lock_acquire kernel/locking/lockdep.c:5842 [inline]
 lock_acquire+0xfc/0x330 kernel/locking/lockdep.c:5825
 __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:274 [inline]
 p9_req_put net/9p/client.c:282 [inline]
 p9_req_put+0xaf/0x250 net/9p/client.c:279
 req_done+0x1dc/0x2e0 net/9p/trans_virtio.c:147
 vring_interrupt+0x2cf/0x440 drivers/virtio/virtio_ring.c:2718
 __handle_irq_event_percpu+0x236/0x890 kernel/irq/handle.c:211
 handle_irq_event_percpu kernel/irq/handle.c:248 [inline]
 handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:265
 handle_edge_irq+0x3ca/0x9e0 kernel/irq/chip.c:855
 generic_handle_irq_desc include/linux/irqdesc.h:172 [inline]
 handle_irq arch/x86/kernel/irq.c:255 [inline]
 call_irq_handler arch/x86/kernel/irq.c:311 [inline]
 __common_interrupt+0xd0/0x2f0 arch/x86/kernel/irq.c:326
 common_interrupt+0xba/0xe0 arch/x86/kernel/irq.c:319
 </IRQ>
 <TASK>
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
RIP: 0010:__sanitizer_cov_trace_switch+0x40/0x90 kernel/kcov.c:351
Code: 48 83 f8 20 74 6b 77 48 48 83 f8 08 74 5b 48 83 f8 10 75 2f 41 bd 03 00 00 00 4c 8b 75 00 31 db 4d 85 f6 74 1e 48 8b 74 dd 10 <48> 8b 4c 24 28 4c 89 e2 4c 89 ef 48 83 c3 01 e8 8c fd ff ff 49 39
RSP: 0018:ffffc9000e317d58 EFLAGS: 00000202
RAX: 0000000000000000 RBX: 0000000000000002 RCX: ffffffff81b1910a
RDX: ffff88804bbac980 RSI: 0000000000000003 RDI: 0000000000000005
RBP: ffffffff8b9100a0 R08: 0000000000000005 R09: 0000000000000001
R10: 0000000000000000 R11: ffff88804bbad4b0 R12: 0000000000000000
R13: 0000000000000005 R14: 000000000000000d R15: 0000000000000000
 do_futex+0xda/0x350 kernel/futex/syscalls.c:125
 __do_sys_futex kernel/futex/syscalls.c:207 [inline]
 __se_sys_futex kernel/futex/syscalls.c:188 [inline]
 __x64_sys_futex+0x1e0/0x4c0 kernel/futex/syscalls.c:188
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f095a58f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff6401b3e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00000000000a3027 RCX: 00007f095a58f7c9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f095a7e5fac
RBP: 0000000000000032 R08: 00007f095b383000 R09: 000000036401b6df
R10: 00007fff6401b4e0 R11: 0000000000000246 R12: 00007f095a7e5fac
R13: 00007fff6401b4e0 R14: 00000000000a3059 R15: 00007fff6401b500
 </TASK>

Allocated by task 27675:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kmalloc_noprof include/linux/slab.h:957 [inline]
 p9_client_create+0xae/0xe40 net/9p/client.c:862
 v9fs_session_init+0x40/0xd40 fs/9p/v9fs.c:442
 v9fs_get_tree+0xb8/0xb50 fs/9p/vfs_super.c:97
 vfs_get_tree+0x8e/0x330 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount fs/namespace.c:3712 [inline]
 path_mount+0x7bf/0x23a0 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount fs/namespace.c:4201 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:4201
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 27675:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6674 [inline]
 kfree+0x2f8/0x6e0 mm/slub.c:6882
 p9_client_create+0x6c5/0xe40 net/9p/client.c:941
 v9fs_session_init+0x40/0xd40 fs/9p/v9fs.c:442
 v9fs_get_tree+0xb8/0xb50 fs/9p/vfs_super.c:97
 vfs_get_tree+0x8e/0x330 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount fs/namespace.c:3712 [inline]
 path_mount+0x7bf/0x23a0 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount fs/namespace.c:4201 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:4201
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88805500e800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
 freed 512-byte region [ffff88805500e800, ffff88805500ea00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88805500f400 pfn:0x5500c
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b442c80 0000000000000000 dead000000000001
raw: ffff88805500f400 000000008010000f 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b442c80 0000000000000000 dead000000000001
head: ffff88805500f400 000000008010000f 00000000f5000000 0000000000000000
head: 00fff00000000002 ffffea0001540301 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5942, tgid 5942 (syz-executor), ts 65586691460, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1af/0x220 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0xd0b/0x31a0 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x25f/0x2430 mm/page_alloc.c:5240
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab mm/slub.c:3248 [inline]
 new_slab+0x2c3/0x430 mm/slub.c:3302
 ___slab_alloc+0xe18/0x1c90 mm/slub.c:4656
 __slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 __do_kmalloc_node mm/slub.c:5656 [inline]
 __kmalloc_noprof+0x4fc/0x910 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 fib6_info_alloc+0x40/0x160 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x14c/0xaa0 net/ipv6/route.c:3820
 ip6_route_add.part.0+0x22/0x1d0 net/ipv6/route.c:3949
 ip6_route_add+0x45/0x60 net/ipv6/route.c:3946
 addrconf_prefix_route+0x2fd/0x510 net/ipv6/addrconf.c:2488
 fixup_permanent_addr net/ipv6/addrconf.c:3598 [inline]
 addrconf_permanent_addr net/ipv6/addrconf.c:3622 [inline]
 addrconf_notify+0x12be/0x19f0 net/ipv6/addrconf.c:3694
 notifier_call_chain+0xbc/0x3e0 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x110 net/core/dev.c:2243
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88805500e700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88805500e780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805500e800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88805500e880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805500e900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
----------------
Code disassembly (best guess):
   0:	48 83 f8 20          	cmp    $0x20,%rax
   4:	74 6b                	je     0x71
   6:	77 48                	ja     0x50
   8:	48 83 f8 08          	cmp    $0x8,%rax
   c:	74 5b                	je     0x69
   e:	48 83 f8 10          	cmp    $0x10,%rax
  12:	75 2f                	jne    0x43
  14:	41 bd 03 00 00 00    	mov    $0x3,%r13d
  1a:	4c 8b 75 00          	mov    0x0(%rbp),%r14
  1e:	31 db                	xor    %ebx,%ebx
  20:	4d 85 f6             	test   %r14,%r14
  23:	74 1e                	je     0x43
  25:	48 8b 74 dd 10       	mov    0x10(%rbp,%rbx,8),%rsi
* 2a:	48 8b 4c 24 28       	mov    0x28(%rsp),%rcx <-- trapping instruction
  2f:	4c 89 e2             	mov    %r12,%rdx
  32:	4c 89 ef             	mov    %r13,%rdi
  35:	48 83 c3 01          	add    $0x1,%rbx
  39:	e8 8c fd ff ff       	call   0xfffffdca
  3e:	49                   	rex.WB
  3f:	39                   	.byte 0x39