==================================================================
BUG: KASAN: use-after-free in string_nocheck lib/vsprintf.c:641 [inline]
BUG: KASAN: use-after-free in string+0x21f/0x2b0 lib/vsprintf.c:723
Read of size 1 at addr ffff8881169a3cb9 by task syz.7.1331/5426

CPU: 0 PID: 5426 Comm: syz.7.1331 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:306
 string_nocheck lib/vsprintf.c:641 [inline]
 string+0x21f/0x2b0 lib/vsprintf.c:723
 vsnprintf+0xf20/0x1960 lib/vsprintf.c:2689
 seq_vprintf fs/seq_file.c:398 [inline]
 seq_printf+0x175/0x260 fs/seq_file.c:413
 input_devices_seq_show+0x1a6/0x650 drivers/input/input.c:1186
 seq_read_iter+0x93f/0xd30 fs/seq_file.c:272
 seq_read+0x3cc/0x4d0 fs/seq_file.c:162
 pde_read fs/proc/inode.c:321 [inline]
 proc_reg_read+0x1c4/0x2b0 fs/proc/inode.c:333
 vfs_read+0x1fe/0xa10 fs/read_write.c:494
 ksys_read+0x140/0x240 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:642
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fe7a802eba9
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:00007fe7a6a97038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fe7a8275fa0 RCX: 00007fe7a802eba9
RDX: 0000000000002020 RSI: 000020000000ac40 RDI: 0000000000000004
RBP: 00007fe7a80b1e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe7a8276038 R14: 00007fe7a8275fa0 R15: 00007ffe58f0b3d8

Allocated by task 1224:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 ____kasan_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xda/0x110 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 __kmalloc+0x1a7/0x330 mm/slub.c:4038
 kmalloc include/linux/slab.h:557 [inline]
 kzalloc include/linux/slab.h:664 [inline]
 neigh_alloc net/core/neighbour.c:439 [inline]
 ___neigh_create+0x6f0/0x1a20 net/core/neighbour.c:592
 __neigh_create+0x31/0x40 net/core/neighbour.c:680
 ip6_finish_output2+0x8d1/0x1500 net/ipv6/ip6_output.c:127
 __ip6_finish_output+0x5ff/0x790 net/ipv6/ip6_output.c:201
 ip6_finish_output+0x33/0x1f0 net/ipv6/ip6_output.c:211
 NF_HOOK_COND include/linux/netfilter.h:288 [inline]
 ip6_output+0x1d1/0x3b0 net/ipv6/ip6_output.c:234
 dst_output include/net/dst.h:451 [inline]
 NF_HOOK include/linux/netfilter.h:299 [inline]
 ndisc_send_skb+0x6f5/0xb40 net/ipv6/ndisc.c:513
 ndisc_send_rs+0x6e5/0x960 net/ipv6/ndisc.c:707
 addrconf_dad_completed+0x97f/0xe80 net/ipv6/addrconf.c:4287
 addrconf_dad_work+0xc18/0x1410 net/ipv6/addrconf.c:-1
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Freed by task 77:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kfree+0xc0/0x270 mm/slub.c:4196
 skb_free_head net/core/skbuff.c:606 [inline]
 skb_release_data+0x532/0x670 net/core/skbuff.c:626
 skb_release_all net/core/skbuff.c:680 [inline]
 __kfree_skb net/core/skbuff.c:694 [inline]
 consume_skb+0xab/0x1f0 net/core/skbuff.c:851
 skb_free_datagram+0x28/0xe0 net/core/datagram.c:325
 unix_dgram_recvmsg+0x9c0/0xd40 net/unix/af_unix.c:2233
 sock_recvmsg_nosec net/socket.c:905 [inline]
 sock_recvmsg net/socket.c:923 [inline]
 sock_read_iter+0x2a2/0x340 net/socket.c:996
 call_read_iter include/linux/fs.h:2060 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x874/0xa10 fs/read_write.c:496
 ksys_read+0x140/0x240 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:642
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 kvfree_call_rcu+0x10c/0x620 kernel/rcu/tree.c:3539
 neigh_destroy+0x445/0x570 net/core/neighbour.c:865
 neigh_release include/net/neighbour.h:427 [inline]
 neigh_cleanup_and_release+0x76/0x1a0 net/core/neighbour.c:104
 neigh_flush_dev+0x642/0x820 net/core/neighbour.c:375
 __neigh_ifdown+0x3f/0x380 net/core/neighbour.c:392
 neigh_ifdown+0x1f/0x30 net/core/neighbour.c:409
 rt6_disable_ip+0x616/0x6a0 net/ipv6/route.c:4802
 addrconf_ifdown+0x144/0x1800 net/ipv6/addrconf.c:3788
 addrconf_notify+0x3bd/0xe90 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410
 call_netdevice_notifiers_info net/core/dev.c:2054 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2066 [inline]
 call_netdevice_notifiers net/core/dev.c:2080 [inline]
 dev_close_many+0x330/0x4d0 net/core/dev.c:1655
 unregister_netdevice_many+0x44c/0x1980 net/core/dev.c:10744
 default_device_exit_batch+0x330/0x390 net/core/dev.c:11287
 ops_exit_list net/core/net_namespace.c:190 [inline]
 cleanup_net+0x5fb/0xb70 net/core/net_namespace.c:609
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

The buggy address belongs to the object at ffff8881169a3c00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 185 bytes inside of
 512-byte region [ffff8881169a3c00, ffff8881169a3e00)
The buggy address belongs to the page:
page:ffffea00045a6800 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8881169a1c00 pfn:0x1169a0
head:ffffea00045a6800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea0004327608 ffffea00042ec908 ffff888100043080
raw: ffff8881169a1c00 000000000010000a 00000001ffffffff 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 99, ts 5053819542, free_ts 0
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5370
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 __kmalloc_track_caller+0x1ef/0x320 mm/slub.c:4541
 __kmalloc_reserve net/core/skbuff.c:144 [inline]
 __alloc_skb+0xdc/0x520 net/core/skbuff.c:212
 alloc_skb include/linux/skbuff.h:1126 [inline]
 alloc_skb_with_frags+0xa2/0x560 net/core/skbuff.c:5993
 sock_alloc_send_pskb+0x853/0x980 net/core/sock.c:2388
 unix_dgram_sendmsg+0x5f4/0x17d0 net/unix/af_unix.c:1725
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 sock_write_iter+0x29c/0x380 net/socket.c:1018
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x725/0xd60 fs/read_write.c:605
 ksys_write+0x140/0x240 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881169a3b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881169a3c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881169a3c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff8881169a3d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881169a3d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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