4.14-stable review patch. If anyone has any objections, please let me know.
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From: Subash Abhinov Kasiviswanathan subashab@codeaurora.org
commit 32c1733f0dd4bd11d6e65512bf4dc337c0452c8e upstream.
skb_header_pointer will copy data into a buffer if data is non linear, otherwise it will return a pointer in the linear section of the data. nf_sk_lookup_slow_v{4,6} always copies data of size udphdr but later accesses memory within the size of tcphdr (th->doff) in case of TCP packets. This causes a crash when running with KASAN with the following call stack -
BUG: KASAN: stack-out-of-bounds in xt_socket_lookup_slow_v4+0x524/0x718 net/netfilter/xt_socket.c:178 Read of size 2 at addr ffffffe3d417a87c by task syz-executor/28971 CPU: 2 PID: 28971 Comm: syz-executor Tainted: G B W O 4.9.65+ #1 Call trace: [<ffffff9467e8d390>] dump_backtrace+0x0/0x428 arch/arm64/kernel/traps.c:76 [<ffffff9467e8d7e0>] show_stack+0x28/0x38 arch/arm64/kernel/traps.c:226 [<ffffff946842d9b8>] __dump_stack lib/dump_stack.c:15 [inline] [<ffffff946842d9b8>] dump_stack+0xd4/0x124 lib/dump_stack.c:51 [<ffffff946811d4b0>] print_address_description+0x68/0x258 mm/kasan/report.c:248 [<ffffff946811d8c8>] kasan_report_error mm/kasan/report.c:347 [inline] [<ffffff946811d8c8>] kasan_report.part.2+0x228/0x2f0 mm/kasan/report.c:371 [<ffffff946811df44>] kasan_report+0x5c/0x70 mm/kasan/report.c:372 [<ffffff946811bebc>] check_memory_region_inline mm/kasan/kasan.c:308 [inline] [<ffffff946811bebc>] __asan_load2+0x84/0x98 mm/kasan/kasan.c:739 [<ffffff94694d6f04>] __tcp_hdrlen include/linux/tcp.h:35 [inline] [<ffffff94694d6f04>] xt_socket_lookup_slow_v4+0x524/0x718 net/netfilter/xt_socket.c:178
Fix this by copying data into appropriate size headers based on protocol.
Fixes: a583636a83ea ("inet: refactor inet[6]_lookup functions to take skb") Signed-off-by: Tejaswi Tanikella tejaswit@codeaurora.org Signed-off-by: Subash Abhinov Kasiviswanathan subashab@codeaurora.org Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/ipv4/netfilter/nf_socket_ipv4.c | 6 ++++-- net/ipv6/netfilter/nf_socket_ipv6.c | 6 ++++-- 2 files changed, 8 insertions(+), 4 deletions(-)
--- a/net/ipv4/netfilter/nf_socket_ipv4.c +++ b/net/ipv4/netfilter/nf_socket_ipv4.c @@ -108,10 +108,12 @@ struct sock *nf_sk_lookup_slow_v4(struct int doff = 0;
if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { - struct udphdr _hdr, *hp; + struct tcphdr _hdr; + struct udphdr *hp;
hp = skb_header_pointer(skb, ip_hdrlen(skb), - sizeof(_hdr), &_hdr); + iph->protocol == IPPROTO_UDP ? + sizeof(*hp) : sizeof(_hdr), &_hdr); if (hp == NULL) return NULL;
--- a/net/ipv6/netfilter/nf_socket_ipv6.c +++ b/net/ipv6/netfilter/nf_socket_ipv6.c @@ -116,9 +116,11 @@ struct sock *nf_sk_lookup_slow_v6(struct }
if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) { - struct udphdr _hdr, *hp; + struct tcphdr _hdr; + struct udphdr *hp;
- hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); + hp = skb_header_pointer(skb, thoff, tproto == IPPROTO_UDP ? + sizeof(*hp) : sizeof(_hdr), &_hdr); if (hp == NULL) return NULL;