[PATCH] tcp_sendpage(): fix broken page iteration

[Dan Aloni <da-x@monatomic.org>]

do_tcp_sendpages() should not iterate 'pages' as an array since 
it is not an array of 'struct page *', but a pointer to a single 
entity of 'struct page *' passed on the stack as a parameter to 
tcp_send_page() (hence it would crash if poffset + psize > PAGE_SIZE,
because pages[1] and beyond most probably not constitutes a valid 
'struct page *').

Since 'page' points to an array of 'struct page', the obvious fix 
is to iterate that array instead, and that's what the function
should have done in the first place.

Applies to 2.6.21-rc4 and above.


diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 3834b10..4881c8d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -501,7 +501,7 @@ static inline void tcp_push(struct sock *sk, struct tcp_sock *tp, int flags,
 	}
 }
 
-static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffset,
+static ssize_t do_tcp_sendpages(struct sock *sk, struct page *pages, int poffset,
 			 size_t psize, int flags)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -527,7 +527,7 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffse
 
 	while (psize > 0) {
 		struct sk_buff *skb = sk->sk_write_queue.prev;
-		struct page *page = pages[poffset / PAGE_SIZE];
+		struct page *page = &pages[poffset / PAGE_SIZE];
 		int copy, i, can_coalesce;
 		int offset = poffset % PAGE_SIZE;
 		int size = min_t(size_t, psize, PAGE_SIZE - offset);
@@ -630,7 +630,7 @@ ssize_t tcp_sendpage(struct socket *sock, struct page *page, int offset,
 
 	lock_sock(sk);
 	TCP_CHECK_TIMER(sk);
-	res = do_tcp_sendpages(sk, &page, offset, size, flags);
+	res = do_tcp_sendpages(sk, page, offset, size, flags);
 	TCP_CHECK_TIMER(sk);
 	release_sock(sk);
 	return res;


-- 
Dan Aloni
XIV LTD, http://www.xivstorage.com
da-x (at) monatomic.org, dan (at) xiv.co.il