Messages in this thread | | | Subject | Re: [PATCH] net: sock: validate data_len before allocating skb in sock_alloc_send_pskb() | From | Eric Dumazet <> | Date | Wed, 30 May 2012 08:46:23 +0200 |
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On Wed, 2012-05-30 at 13:47 +0800, Jason Wang wrote: > 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. > > Cc: stable@vger.kernel.org [2.6.27+] > Signed-off-by: Jason Wang <jasowang@redhat.com> > --- > net/core/sock.c | 8 ++++++-- > 1 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/net/core/sock.c b/net/core/sock.c > index 653f8c0..4ad5fa5 100644 > --- a/net/core/sock.c > +++ b/net/core/sock.c > @@ -1599,6 +1599,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len, > > timeo = sock_sndtimeo(sk, noblock); > while (1) { > + int npages; > err = sock_error(sk); > if (err != 0) > goto failure; > @@ -1607,17 +1608,20 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len, > if (sk->sk_shutdown & SEND_SHUTDOWN) > goto failure; > > + err = -EMSGSIZE; > + npages = (data_len + (PAGE_SIZE - 1)) >> PAGE_SHIFT; > + if (npages > MAX_SKB_FRAGS) > + goto failure; > + > 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++) { >
Why doing this test in the while (1) block, it should be done before the loop...
Or even in the caller, note net/unix/af_unix.c does this right.
if (len > SKB_MAX_ALLOC) data_len = min_t(size_t, len - SKB_MAX_ALLOC, MAX_SKB_FRAGS * PAGE_SIZE);
skb = sock_alloc_send_pskb(sk, len - data_len, data_len, msg->msg_flags & MSG_DONTWAIT, &err);
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