syzbot

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
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BUG: KASAN: slab-out-of-bounds in ip6_dst_idev include/net/ip6_fib.h:141 [inline]
BUG: KASAN: slab-out-of-bounds in ip6_xmit+0x1838/0x1b80 net/ipv6/ip6_output.c:254
Read of size 8 at addr ffff8801cf47b798 by task syz-executor243/3776

CPU: 1 PID: 3776 Comm: syz-executor243 Not tainted 4.9.123-g7fa8c15 #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801babf7540 ffffffff81eb9689 ffffea00073d1ec0 ffff8801cf47b798
 0000000000000000 ffff8801cf47b798 0000000000000040 ffff8801babf7578
 ffffffff8156c3fe ffff8801cf47b798 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81eb9689>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb9689>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8156c3fe>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff8156c808>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff8156c808>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153fb94>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 [<ffffffff835625a8>] ip6_dst_idev include/net/ip6_fib.h:141 [inline]
 [<ffffffff835625a8>] ip6_xmit+0x1838/0x1b80 net/ipv6/ip6_output.c:254
 [<ffffffff8362782c>] inet6_csk_xmit+0x27c/0x4d0 net/ipv6/inet6_connection_sock.c:178
 [<ffffffff836c4665>] l2tp_xmit_core net/l2tp/l2tp_core.c:1178 [inline]
 [<ffffffff836c4665>] l2tp_xmit_skb+0xc45/0xf30 net/l2tp/l2tp_core.c:1273
 [<ffffffff836cfc30>] pppol2tp_sendmsg+0x4e0/0x790 net/l2tp/l2tp_ppp.c:339
 [<ffffffff8301e0ac>] sock_sendmsg_nosec net/socket.c:648 [inline]
 [<ffffffff8301e0ac>] sock_sendmsg+0xcc/0x110 net/socket.c:658
 [<ffffffff8301f8ca>] ___sys_sendmsg+0x47a/0x840 net/socket.c:1982
 [<ffffffff83021e31>] __sys_sendmmsg+0x161/0x3d0 net/socket.c:2072
 [<ffffffff830220d5>] SYSC_sendmmsg net/socket.c:2103 [inline]
 [<ffffffff830220d5>] SyS_sendmmsg+0x35/0x60 net/socket.c:2098
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a01d93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801cf47b780
 which belongs to the cache ip_dst_cache of size 216
The buggy address is located 24 bytes inside of
 216-byte region [ffff8801cf47b780, ffff8801cf47b858)
The buggy address belongs to the page:
page:ffffea00073d1ec0 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0x8000000000000080(slab)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cf47b680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801cf47b700: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801cf47b780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff8801cf47b800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801cf47b880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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