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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 ffff8881281074b9 by task syz.1.2481/9449

CPU: 0 PID: 9449 Comm: syz.1.2481 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: 0033:0x7f4f017ffba9
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:00007f4f00268038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f4f01a46fa0 RCX: 00007f4f017ffba9
RDX: 0000000000002020 RSI: 0000200000004480 RDI: 0000000000000005
RBP: 00007f4f01882e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4f01a47038 R14: 00007f4f01a46fa0 R15: 00007fff7916dd48

Allocated by task 2101:
 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]
 kmem_cache_alloc_trace+0x184/0x2e0 mm/slub.c:2979
 kmalloc include/linux/slab.h:552 [inline]
 kmalloc_array include/linux/slab.h:591 [inline]
 rtnl_newlink+0x103/0x1640 net/core/rtnetlink.c:3526
 rtnetlink_rcv_msg+0x9db/0xb90 net/core/rtnetlink.c:5610
 netlink_rcv_skb+0x1e0/0x430 net/netlink/af_netlink.c:2503
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5628
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x876/0xa40 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x88d/0xb30 net/netlink/af_netlink.c:1914
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 __sys_sendto+0x41d/0x580 net/socket.c:2006
 __do_sys_sendto net/socket.c:2018 [inline]
 __se_sys_sendto net/socket.c:2014 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2014
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 8858:
 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]
 kfree_skb+0xb9/0x2f0 net/core/skbuff.c:713
 vti6_tnl_xmit+0xe70/0x15c0 net/ipv6/ip6_vti.c:593
 __netdev_start_xmit include/linux/netdevice.h:4864 [inline]
 netdev_start_xmit include/linux/netdevice.h:4878 [inline]
 xmit_one net/core/dev.c:3608 [inline]
 dev_hard_start_xmit+0x244/0x670 net/core/dev.c:3624
 __dev_queue_xmit+0x1446/0x2540 net/core/dev.c:4210
 dev_queue_xmit+0x17/0x20 net/core/dev.c:4243
 neigh_connected_output+0x432/0x460 net/core/neighbour.c:1538
 neigh_output include/net/neighbour.h:517 [inline]
 ip_finish_output2+0xad5/0xec0 net/ipv4/ip_output.c:237
 __ip_finish_output+0x3fb/0x720 net/ipv4/ip_output.c:-1
 ip_finish_output+0x33/0x1f0 net/ipv4/ip_output.c:325
 NF_HOOK_COND include/linux/netfilter.h:288 [inline]
 ip_output+0x1e1/0x360 net/ipv4/ip_output.c:439
 dst_output include/net/dst.h:451 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 ip_send_skb net/ipv4/ip_output.c:1591 [inline]
 ip_push_pending_frames+0x2c3/0x540 net/ipv4/ip_output.c:1611
 raw_sendmsg+0xdd7/0x1270 net/ipv4/raw.c:676
 inet_sendmsg+0xa5/0xc0 net/ipv4/af_inet.c:830
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 ____sys_sendmsg+0x5a2/0x8c0 net/socket.c:2376
 ___sys_sendmsg+0x1f0/0x260 net/socket.c:2430
 __sys_sendmmsg+0x273/0x450 net/socket.c:2516
 __do_sys_sendmmsg net/socket.c:2545 [inline]
 __se_sys_sendmmsg net/socket.c:2542 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2542
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff888128107400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 185 bytes inside of
 512-byte region [ffff888128107400, ffff888128107600)
The buggy address belongs to the page:
page:ffffea0004a04100 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x128104
head:ffffea0004a04100 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea00049a0d00 0000000400000004 ffff888100043080
raw: 0000000000000000 0000000000100010 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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 289, ts 26635838843, 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]
 ndisc_alloc_skb net/ipv6/ndisc.c:422 [inline]
 ndisc_send_rs+0x2ce/0x960 net/ipv6/ndisc.c:691
 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
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888128107380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888128107400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888128107480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff888128107500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888128107580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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