[TCP]: Fix sk_forward_alloc underflow in tcp_sendmsg
I've finally found a potential cause of the sk_forward_alloc underflows
that people have been reporting sporadically.
When tcp_sendmsg tacks on extra bits to an existing TCP_PAGE we don't
check sk_forward_alloc even though a large amount of time may have
elapsed since we allocated the page. In the mean time someone could've
come along and liberated packets and reclaimed sk_forward_alloc memory.
This patch makes tcp_sendmsg check sk_forward_alloc every time as we
do in do_tcp_sendpages.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 854f6d0..cbcc9fc 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -769,19 +769,23 @@
if (off == PAGE_SIZE) {
put_page(page);
TCP_PAGE(sk) = page = NULL;
+ TCP_OFF(sk) = off = 0;
}
- }
+ } else
+ BUG_ON(off);
+
+ if (copy > PAGE_SIZE - off)
+ copy = PAGE_SIZE - off;
+
+ if (!sk_stream_wmem_schedule(sk, copy))
+ goto wait_for_memory;
if (!page) {
/* Allocate new cache page. */
if (!(page = sk_stream_alloc_page(sk)))
goto wait_for_memory;
- off = 0;
}
- if (copy > PAGE_SIZE - off)
- copy = PAGE_SIZE - off;
-
/* Time to copy data. We are close to
* the end! */
err = skb_copy_to_page(sk, from, skb, page,