KASAN: use-after-free Read in ip6_xmit

[syzbot]

Hello,

syzkaller hit the following crash on
0e08c463db387a2adcb0243b15ab868a73f87807
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


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Reported-by: syzbot+56029f...@syzkaller.appspotmail.com
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audit: type=1400 audit(1514737122.010:7): avc: denied { map } for
pid=3153 comm="syzkaller920384" path="/root/syzkaller920384627" dev="sda1"
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:189
[inline]
BUG: KASAN: use-after-free in ip6_xmit+0x1f92/0x1fc0
net/ipv6/ip6_output.c:248
Read of size 8 at addr ffff8801ca6f9f18 by task syzkaller920384/3153

CPU: 1 PID: 3153 Comm: syzkaller920384 Not tainted
4.15.0-rc4-next-20171221+ #78
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x25b/0x340 mm/kasan/report.c:409
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
ip6_dst_idev include/net/ip6_fib.h:189 [inline]
ip6_xmit+0x1f92/0x1fc0 net/ipv6/ip6_output.c:248
inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
tcp_transmit_skb+0x1b12/0x38b0 net/ipv4/tcp_output.c:1176
tcp_send_syn_data net/ipv4/tcp_output.c:3456 [inline]
tcp_connect+0x1ed5/0x4090 net/ipv4/tcp_output.c:3495
tcp_v4_connect+0x15ef/0x1e70 net/ipv4/tcp_ipv4.c:257
__inet_stream_connect+0x2d4/0xf00 net/ipv4/af_inet.c:620
tcp_sendmsg_fastopen net/ipv4/tcp.c:1167 [inline]
tcp_sendmsg_locked+0x27e4/0x3b30 net/ipv4/tcp.c:1212
tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1459
inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:764
sock_sendmsg_nosec net/socket.c:628 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:638
SYSC_sendto+0x361/0x5c0 net/socket.c:1719
SyS_sendto+0x40/0x50 net/socket.c:1687
entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x43fda9
RSP: 002b:00007ffc9b8bd818 EFLAGS: 00000217 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 000000000043fda9
RDX: 0000000000000000 RSI: 0000000020aa1000 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000020aa1000 R09: 0000000000000010
R10: 0000000023ffffff R11: 0000000000000217 R12: 0000000000401710
R13: 00000000004017a0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3140:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3545
dst_alloc+0x11f/0x1a0 net/core/dst.c:104
rt_dst_alloc+0xe9/0x520 net/ipv4/route.c:1500
__mkroute_output net/ipv4/route.c:2242 [inline]
ip_route_output_key_hash_rcu+0xa40/0x2c10 net/ipv4/route.c:2470
ip_route_output_key_hash+0x20b/0x370 net/ipv4/route.c:2299
__ip_route_output_key include/net/route.h:125 [inline]
ip_route_connect include/net/route.h:300 [inline]
__ip4_datagram_connect+0xa67/0x1240 net/ipv4/datagram.c:51
__ip6_datagram_connect+0x709/0xf90 net/ipv6/datagram.c:157
ip6_datagram_connect+0x2f/0x50 net/ipv6/datagram.c:274
inet_dgram_connect+0x16b/0x1f0 net/ipv4/af_inet.c:542
SYSC_connect+0x213/0x4a0 net/socket.c:1611
SyS_connect+0x24/0x30 net/socket.c:1592
entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 0:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3489 [inline]
kmem_cache_free+0x83/0x2a0 mm/slab.c:3747
dst_destroy+0x219/0x310 net/core/dst.c:140
dst_destroy_rcu+0x16/0x20 net/core/dst.c:153
__rcu_reclaim kernel/rcu/rcu.h:172 [inline]
rcu_do_batch kernel/rcu/tree.c:2675 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2934 [inline]
__rcu_process_callbacks kernel/rcu/tree.c:2901 [inline]
rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2918
__do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801ca6f9f00
which belongs to the cache ip_dst_cache of size 168
The buggy address is located 24 bytes inside of
168-byte region [ffff8801ca6f9f00, ffff8801ca6f9fa8)
The buggy address belongs to the page:
page:00000000637e5443 count:1 mapcount:0 mapping:0000000000ddf2d5
index:0xffff8801ca6f9000
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801ca6f9000 ffff8801ca6f9000 000000010000000a
raw: ffff8801d794f138 ffffea0007515320 ffff8801d6d724c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801ca6f9e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801ca6f9e80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
> ffff8801ca6f9f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801ca6f9f80: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
ffff8801ca6fa000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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[Eric Biggers]

No longer reproducible, seems to have first fixed by commit d91c3e17f75f21
("net/tls: Only attach to sockets in ESTABLISHED state"), but commit
c113187d38ff85d ("tls: Use correct sk->sk_prot for IPV6") also appears related.
That fixes it too if I revert the first commit, and the KASAN report indicates
that an 'struct rtable' (IPv4-related) was accessed as if it were an
'struct rt6_info' (IPv6-related). So telling syzbot:

#syz fix: tls: Use correct sk->sk_prot for IPV6

I also had simplified this reproducer a bit, so I'm pasting it below in case
anyone still wants it:

#include <netinet/in.h>
#include <unistd.h>

#define SOL_TCP 6
#define TCP_ULP 31

int main()
{
int tcp_fd;
struct sockaddr_in addr = {
.sin_family = AF_INET,
.sin_port = htobe16(0x4e22),
.sin_addr = { htobe32(0x7f000001) }
};

tcp_fd = socket(AF_INET6, SOCK_STREAM, 0);
setsockopt(tcp_fd, SOL_TCP, TCP_ULP, "tls", 4);
sendto(tcp_fd, NULL, 0, MSG_FASTOPEN, (void *)&addr, sizeof(addr));
}

- Eric