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From c3bfbecb1bb575278ce4812746a29c04875a2926 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 30 Dec 2015 08:51:12 -0500
Subject: udp: properly support MSG_PEEK with truncated buffers
commit 197c949e7798fbf28cfadc69d9ca0c2abbf93191 upstream.
Backport of this upstream commit into stable kernels :
89c22d8c3b27 ("net: Fix skb csum races when peeking")
exposed a bug in udp stack vs MSG_PEEK support, when user provides
a buffer smaller than skb payload.
In this case,
skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr),
msg->msg_iov);
returns -EFAULT.
This bug does not happen in upstream kernels since Al Viro did a great
job to replace this into :
skb_copy_and_csum_datagram_msg(skb, sizeof(struct udphdr), msg);
This variant is safe vs short buffers.
For the time being, instead reverting Herbert Xu patch and add back
skb->ip_summed invalid changes, simply store the result of
udp_lib_checksum_complete() so that we avoid computing the checksum a
second time, and avoid the problematic
skb_copy_and_csum_datagram_iovec() call.
This patch can be applied on recent kernels as it avoids a double
checksumming, then backported to stable kernels as a bug fix.
CVE: CVE-2016-10229
Upstream-Status: Backport
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
---
net/ipv4/udp.c | 6 ++++--
net/ipv6/udp.c | 6 ++++--
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 4908eaa..f8e3046 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1210,6 +1210,7 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
int peeked, off = 0;
int err;
int is_udplite = IS_UDPLITE(sk);
+ bool checksum_valid = false;
bool slow;
if (flags & MSG_ERRQUEUE)
@@ -1235,11 +1236,12 @@ 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_iovec(skb, sizeof(struct udphdr),
msg->msg_iov, copied);
else {
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index a6c5ef5..94ca417 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -371,6 +371,7 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
int peeked, off = 0;
int err;
int is_udplite = IS_UDPLITE(sk);
+ bool checksum_valid = false;
int is_udp4;
bool slow;
@@ -402,11 +403,12 @@ 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_iovec(skb, sizeof(struct udphdr),
msg->msg_iov, copied);
else {
--
cgit v1.1
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