net: fix nulls list corruptions in sk_prot_alloc

Special care is taken inside sk_port_alloc to avoid overwriting
skc_node/skc_nulls_node. We should also avoid overwriting
skc_bind_node/skc_portaddr_node.

The patch fixes the following crash:

 BUG: unable to handle kernel paging request at fffffffffffffff0
 IP: [<ffffffff812ec6dd>] udp4_lib_lookup2+0xad/0x370
 [<ffffffff812ecc22>] __udp4_lib_lookup+0x282/0x360
 [<ffffffff812ed63e>] __udp4_lib_rcv+0x31e/0x700
 [<ffffffff812bba45>] ? ip_local_deliver_finish+0x65/0x190
 [<ffffffff812bbbf8>] ? ip_local_deliver+0x88/0xa0
 [<ffffffff812eda35>] udp_rcv+0x15/0x20
 [<ffffffff812bba45>] ip_local_deliver_finish+0x65/0x190
 [<ffffffff812bbbf8>] ip_local_deliver+0x88/0xa0
 [<ffffffff812bb2cd>] ip_rcv_finish+0x32d/0x6f0
 [<ffffffff8128c14c>] ? netif_receive_skb+0x99c/0x11c0
 [<ffffffff812bb94b>] ip_rcv+0x2bb/0x350
 [<ffffffff8128c14c>] netif_receive_skb+0x99c/0x11c0

Signed-off-by: Leonard Crestez <lcrestez@ixiacom.com>
Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 39 insertions, 12 deletions

diff --git a/net/core/sock.c b/net/core/sock.c
index fb6080111461..e5af8d5d5b50 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1009,6 +1009,36 @@ static void sock_copy(struct sock *nsk, const struct sock *osk)
 #endif
 }
 
+/*
+ * caches using SLAB_DESTROY_BY_RCU should let .next pointer from nulls nodes
+ * un-modified. Special care is taken when initializing object to zero.
+ */
+static inline void sk_prot_clear_nulls(struct sock *sk, int size)
+{
+        if (offsetof(struct sock, sk_node.next) != 0)
+                memset(sk, 0, offsetof(struct sock, sk_node.next));
+        memset(&sk->sk_node.pprev, 0,
+               size - offsetof(struct sock, sk_node.pprev));
+}
+
+void sk_prot_clear_portaddr_nulls(struct sock *sk, int size)
+{
+        unsigned long nulls1, nulls2;
+
+        nulls1 = offsetof(struct sock, __sk_common.skc_node.next);
+        nulls2 = offsetof(struct sock, __sk_common.skc_portaddr_node.next);
+        if (nulls1 > nulls2)
+                swap(nulls1, nulls2);
+
+        if (nulls1 != 0)
+                memset((char *)sk, 0, nulls1);
+        memset((char *)sk + nulls1 + sizeof(void *), 0,
+               nulls2 - nulls1 - sizeof(void *));
+        memset((char *)sk + nulls2 + sizeof(void *), 0,
+               size - nulls2 - sizeof(void *));
+}
+EXPORT_SYMBOL(sk_prot_clear_portaddr_nulls);
+
 static struct sock *sk_prot_alloc(struct proto *prot, gfp_t priority,
                 int family)
 {
@@ -1021,19 +1051,12 @@ static struct sock *sk_prot_alloc(struct proto *prot, gfp_t priority,
                 if (!sk)
                         return sk;
                 if (priority & __GFP_ZERO) {
-                        /*
-                         * caches using SLAB_DESTROY_BY_RCU should let
-                         * sk_node.next un-modified. Special care is taken
-                         * when initializing object to zero.
-                         */
-                        if (offsetof(struct sock, sk_node.next) != 0)
-                                memset(sk, 0, offsetof(struct sock, sk_node.next));
-                        memset(&sk->sk_node.pprev, 0,
-                               prot->obj_size - offsetof(struct sock,
-                                                         sk_node.pprev));
+                        if (prot->clear_sk)
+                                prot->clear_sk(sk, prot->obj_size);
+                        else
+                                sk_prot_clear_nulls(sk, prot->obj_size);
                 }
-        }
-        else
+        } else
                 sk = kmalloc(prot->obj_size, priority);
 
         if (sk != NULL) {
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 5e0a3a582a59..2d3ded4d0786 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1899,6 +1899,7 @@ struct proto udp_prot = {
         .compat_setsockopt = compat_udp_setsockopt,
         .compat_getsockopt = compat_udp_getsockopt,
 #endif
+        .clear_sk          = sk_prot_clear_portaddr_nulls,
 };
 EXPORT_SYMBOL(udp_prot);
 
diff --git a/net/ipv4/udplite.c b/net/ipv4/udplite.c
index ab76aa928fa9..aee9963f7f5a 100644
--- a/net/ipv4/udplite.c
+++ b/net/ipv4/udplite.c
@@ -57,6 +57,7 @@ struct proto 	udplite_prot = {
         .compat_setsockopt = compat_udp_setsockopt,
         .compat_getsockopt = compat_udp_getsockopt,
 #endif
+        .clear_sk          = sk_prot_clear_portaddr_nulls,
 };
 EXPORT_SYMBOL(udplite_prot);
 
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 91def93bec85..cd6cb7c3e563 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1477,6 +1477,7 @@ struct proto udpv6_prot = {
         .compat_setsockopt = compat_udpv6_setsockopt,
         .compat_getsockopt = compat_udpv6_getsockopt,
 #endif
+        .clear_sk          = sk_prot_clear_portaddr_nulls,
 };
 
 static struct inet_protosw udpv6_protosw = {
diff --git a/net/ipv6/udplite.c b/net/ipv6/udplite.c
index 5f48fadc27f7..986c4de5292e 100644
--- a/net/ipv6/udplite.c
+++ b/net/ipv6/udplite.c
@@ -55,6 +55,7 @@ struct proto udplitev6_prot = {
         .compat_setsockopt = compat_udpv6_setsockopt,
         .compat_getsockopt = compat_udpv6_getsockopt,
 #endif
+        .clear_sk          = sk_prot_clear_portaddr_nulls,
 };
 
 static struct inet_protosw udplite6_protosw = {