netfilter: xt_socket: Restore mark from full sockets only

An out of bounds error was detected on an ARM64 target with
Android based kernel 4.9. This occurs while trying to
restore mark on a skb from an inet request socket.

BUG: KASAN: slab-out-of-bounds in socket_match.isra.2+0xc8/0x1f0 net/netfilter/xt_socket.c:248
Read of size 4 at addr ffffffc06a8d824c by task syz-fuzzer/1532
CPU: 7 PID: 1532 Comm: syz-fuzzer Tainted: G        W  O    4.9.41+ #1
Call trace:
[<ffffff900808d2f8>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:76
[<ffffff900808d760>] show_stack+0x28/0x38 arch/arm64/kernel/traps.c:226
[<ffffff90085f7dc8>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffff90085f7dc8>] dump_stack+0xe4/0x134 lib/dump_stack.c:51
[<ffffff900830f358>] print_address_description+0x68/0x258 mm/kasan/report.c:248
[<ffffff900830f770>] kasan_report_error mm/kasan/report.c:347 [inline]
[<ffffff900830f770>] kasan_report.part.2+0x228/0x2f0 mm/kasan/report.c:371
[<ffffff900830fdec>] kasan_report+0x5c/0x70 mm/kasan/report.c:372
[<ffffff900830de98>] check_memory_region_inline mm/kasan/kasan.c:308 [inline]
[<ffffff900830de98>] __asan_load4+0x88/0xa0 mm/kasan/kasan.c:740
[<ffffff90097498f8>] socket_match.isra.2+0xc8/0x1f0 net/netfilter/xt_socket.c:248
[<ffffff9009749a5c>] socket_mt4_v1_v2_v3+0x3c/0x48 net/netfilter/xt_socket.c:272
[<ffffff90097f7e4c>] ipt_do_table+0x54c/0xad8 net/ipv4/netfilter/ip_tables.c:311
[<ffffff90097fcf14>] iptable_mangle_hook+0x6c/0x220 net/ipv4/netfilter/iptable_mangle.c:90
...
Allocated by task 1532:
 save_stack_trace_tsk+0x0/0x2a0 arch/arm64/kernel/stacktrace.c:131
 save_stack_trace+0x28/0x38 arch/arm64/kernel/stacktrace.c:215
 save_stack mm/kasan/kasan.c:495 [inline]
 set_track mm/kasan/kasan.c:507 [inline]
 kasan_kmalloc+0xd8/0x188 mm/kasan/kasan.c:599
 kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:537
 slab_post_alloc_hook mm/slab.h:417 [inline]
 slab_alloc_node mm/slub.c:2728 [inline]
 slab_alloc mm/slub.c:2736 [inline]
 kmem_cache_alloc+0x14c/0x2e8 mm/slub.c:2741
 reqsk_alloc include/net/request_sock.h:87 [inline]
 inet_reqsk_alloc+0x4c/0x238 net/ipv4/tcp_input.c:6236
 tcp_conn_request+0x2b0/0xea8 net/ipv4/tcp_input.c:6341
 tcp_v4_conn_request+0xe0/0x100 net/ipv4/tcp_ipv4.c:1256
 tcp_rcv_state_process+0x384/0x18a8 net/ipv4/tcp_input.c:5926
 tcp_v4_do_rcv+0x2f0/0x3e0 net/ipv4/tcp_ipv4.c:1430
 tcp_v4_rcv+0x1278/0x1350 net/ipv4/tcp_ipv4.c:1709
 ip_local_deliver_finish+0x174/0x3e0 net/ipv4/ip_input.c:216

v1->v2: Change socket_mt6_v1_v2_v3() as well as mentioned by Eric
v2->v3: Put the correct fixes tag

Fixes: 01555e74bde5 ("netfilter: xt_socket: add XT_SOCKET_RESTORESKMARK flag")
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/xt_socket.c

@@ -76,7 +76,7 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par,
 			transparent = nf_sk_is_transparent(sk);
 
 		if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
-		    transparent)
+		    transparent && sk_fullsock(sk))
 			pskb->mark = sk->sk_mark;
 
 		if (sk != skb->sk)
@@ -133,7 +133,7 @@ socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
 			transparent = nf_sk_is_transparent(sk);
 
 		if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
-		    transparent)
+		    transparent && sk_fullsock(sk))
 			pskb->mark = sk->sk_mark;
 
 		if (sk != skb->sk)