linux-kernel - [12/26] tcp: fix tcp_md5_hash_skb

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Message-ID: <lsq.1372214158.607250960@decadent.org.uk>
Date:	Wed, 26 Jun 2013 03:35:58 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Bernhard Beck" <bbeck@...gle.com>,
	"Eric Dumazet" <edumazet@...gle.com>,
	"Matt Schnall" <mischnal@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [12/26] tcp: fix tcp_md5_hash_skb_data()

3.2.48-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit 54d27fcb338bd9c42d1dfc5a39e18f6f9d373c2e ]

TCP md5 communications fail [1] for some devices, because sg/crypto code
assume page offsets are below PAGE_SIZE.

This was discovered using mlx4 driver [2], but I suspect loopback
might trigger the same bug now we use order-3 pages in tcp_sendmsg()

[1] Failure is giving following messages.

huh, entered softirq 3 NET_RX ffffffff806ad230 preempt_count 00000100,
exited with 00000101?

[2] mlx4 driver uses order-2 pages to allocate RX frags

Reported-by: Matt Schnall <mischnal@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Bernhard Beck <bbeck@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/ipv4/tcp.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index fe381c2..ec8b4b7e 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3037,8 +3037,11 @@ int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *hp,
 
 	for (i = 0; i < shi->nr_frags; ++i) {
 		const struct skb_frag_struct *f = &shi->frags[i];
-		struct page *page = skb_frag_page(f);
-		sg_set_page(&sg, page, skb_frag_size(f), f->page_offset);
+		unsigned int offset = f->page_offset;
+		struct page *page = skb_frag_page(f) + (offset >> PAGE_SHIFT);
+
+		sg_set_page(&sg, page, skb_frag_size(f),
+			    offset_in_page(offset));
 		if (crypto_hash_update(desc, &sg, skb_frag_size(f)))
 			return 1;
 	}

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