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    Subject[ 29/48] net: sock: validate data_len before allocating skb in sock_alloc_send_pskb()
    3.2-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jason Wang <jasowang@redhat.com>

    [ 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: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/core/sock.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    diff --git a/net/core/sock.c b/net/core/sock.c
    index b23f174..8d095b9 100644
    --- a/net/core/sock.c
    +++ b/net/core/sock.c
    @@ -1497,6 +1497,11 @@ 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)
    @@ -1515,14 +1520,12 @@ 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++) {



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