Re: [PATCH stable <= 3.18] net: add length argument to skb_copy_and_csum_datagram_iovec

On Thu, 2015-11-12 at 10:48 +0100, Sabrina Dubroca wrote:

2015-11-10, 16:03:52 -0800, Greg Kroah-Hartman wrote:

quoted

On Tue, Nov 10, 2015 at 05:59:26PM -0600, Josh Hunt wrote:

quoted

On Thu, Oct 29, 2015 at 5:00 AM, Sabrina Dubroca [off-list ref] wrote:

quoted

2015-10-15, 14:25:03 +0200, Sabrina Dubroca wrote:

quoted

Without this length argument, we can read past the end of the iovec in
memcpy_toiovec because we have no way of knowing the total length of the
iovec's buffers.

This is needed for stable kernels where 89c22d8c3b27 ("net: Fix skb
csum races when peeking") has been backported but that don't have the
ioviter conversion, which is almost all the stable trees <= 3.18.

This also fixes a kernel crash for NFS servers when the client uses
 -onfsvers=3,proto=udp to mount the export.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Hannes Frederic Sowa <redacted>

Fixes CVE-2015-8019.
http://www.openwall.com/lists/oss-security/2015/10/29/1

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Sabrina
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Greg

Do you have this in your queue? I saw a few other stables pick this
up, but haven't seen it in 3.14 or 3.18 yet. It wasn't clear to me if
this had been fully reviewed yet.

I rely on Dave to package up networking stable patches and forward them
on to me, that's why you haven't seen it be picked up yet.

thanks,

greg k-h

David, can you queue this up?

Note that the following patch (and corresponding part for ipv6) might
also have solve the issue ?

This would supposedly save some cycles when MSG_PEEK is used and user
provides short buffers.

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 24ec14f9825c..387acab1ab5c 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c

@@ -1272,6 +1272,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 	int err;
 	int is_udplite = IS_UDPLITE(sk);
 	bool slow;
+	bool checksum_valid = false;
 
 	if (flags & MSG_ERRQUEUE)
 		return ip_recv_error(sk, msg, len, addr_len);

@@ -1296,11 +1297,12 @@ try_again:
 	 */
 
 	if (copied < ulen || UDP_SKB_CB(skb)->partial_cov) {
-		if (udp_lib_checksum_complete(skb))
+		checksum_valid = !udp_lib_checksum_complete(skb);
+		if (!checksum_valid)
 			goto csum_copy_err;
 	}
 
-	if (skb_csum_unnecessary(skb))
+	if (checksum_valid || skb_csum_unnecessary(skb))
 		err = skb_copy_datagram_msg(skb, sizeof(struct udphdr),
 					    msg, copied);
 	else {