net: sock: validate data_len before allocating skb in sock_alloc_send_pskb()

[ Upstream commit cc9b17ad29ecaa20bfe426a8d4dbfb94b13ff1cc ]

We need to validate the number of pages consumed by data_len, otherwise frags
array could be overflowed by userspace. So this patch validate data_len and
return -EMSGSIZE when data_len may occupies more frags than MAX_SKB_FRAGS.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/core/sock.c b/net/core/sock.c
index aebb419519b..b4bb59a9245 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1501,6 +1501,11 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
         gfp_t gfp_mask;
         long timeo;
         int err;
+        int npages = (data_len + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
+
+        err = -EMSGSIZE;
+        if (npages > MAX_SKB_FRAGS)
+                goto failure;
 
         gfp_mask = sk->sk_allocation;
         if (gfp_mask & __GFP_WAIT)
@@ -1519,14 +1524,12 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
                 if (atomic_read(&sk->sk_wmem_alloc) < sk->sk_sndbuf) {
                         skb = alloc_skb(header_len, gfp_mask);
                         if (skb) {
-                                int npages;
                                 int i;
 
                                 /* No pages, we're done... */
                                 if (!data_len)
                                         break;
 
-                                npages = (data_len + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
                                 skb->truesize += data_len;
                                 skb_shinfo(skb)->nr_frags = npages;
                                 for (i = 0; i < npages; i++) {