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BUG: KASAN: use-after-free in ipv6_skip_exthdr+0x4ed/0x520 net/ipv6/exthdrs_core.c:103
Read of size 1 at addr ffff888187430011 by task syz-executor.2/3688

CPU: 0 PID: 3688 Comm: syz-executor.2 Not tainted 6.4.0-rc3-syzkaller-00193-g9b9e46aa0727 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/16/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
 print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
 print_report mm/kasan/report.c:462 [inline]
 kasan_report+0x11c/0x130 mm/kasan/report.c:572
 ipv6_skip_exthdr+0x4ed/0x520 net/ipv6/exthdrs_core.c:103
 ipv6_get_l4proto net/netfilter/nf_conntrack_core.c:393 [inline]
 get_l4proto+0x325/0x500 net/netfilter/nf_conntrack_core.c:416
 nf_conntrack_in+0x264/0x17d0 net/netfilter/nf_conntrack_core.c:1983
 nf_hook_entry_hookfn include/linux/netfilter.h:143 [inline]
 nf_hook_slow+0xc9/0x1f0 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:258 [inline]
 __ip6_local_out+0x3e7/0x8e0 net/ipv6/output_core.c:143
 ip6_local_out+0x2a/0x1a0 net/ipv6/output_core.c:153
 ip6_send_skb+0xbb/0x340 net/ipv6/ip6_output.c:1989
 ip6_push_pending_frames+0xe1/0x110 net/ipv6/ip6_output.c:2009
 l2tp_ip6_push_pending_frames net/l2tp/l2tp_ip6.c:482 [inline]
 l2tp_ip6_sendmsg+0x1724/0x1c50 net/l2tp/l2tp_ip6.c:641
 inet_sendmsg+0x9d/0xe0 net/ipv4/af_inet.c:825
 sock_sendmsg_nosec net/socket.c:724 [inline]
 sock_sendmsg+0xde/0x190 net/socket.c:747
 __sys_sendto+0x23a/0x340 net/socket.c:2144
 __do_sys_sendto net/socket.c:2156 [inline]
 __se_sys_sendto net/socket.c:2152 [inline]
 __x64_sys_sendto+0xe1/0x1b0 net/socket.c:2152
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f398248c169
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f39831d0168 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f39825abf80 RCX: 00007f398248c169
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f39824e7ca1 R08: 0000000020000040 R09: 0000000000000020
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcded0b51f R14: 00007f39831d0300 R15: 0000000000022000
 </TASK>

The buggy address belongs to the physical page:
page:ffffea00061d0c00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x187430
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 057ff00000000000 ffffea00061d0c08 ffffea00061d0c08 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff88818742ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88818742ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888187430000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                         ^
 ffff888187430080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888187430100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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