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authorEric Dumazet <edumazet@google.com>2015-12-30 08:51:12 -0500
committerSasha Levin <alexander.levin@verizon.com>2017-05-28 06:36:10 -0400
commit5c564705d3f0436ddc70d833b975b870ba560528 (patch)
treef67889e9053a26f4bb790801599dc7303283c4c6
parentf97e5ec81364b6edc8d26dfcd0ae43b54d3d43de (diff)
udp: properly support MSG_PEEK with truncated buffers
[ Upstream commit 197c949e7798fbf28cfadc69d9ca0c2abbf93191 ] 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. 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: Sasha Levin <alexander.levin@verizon.com>
-rw-r--r--net/ipv4/udp.c6
-rw-r--r--net/ipv6/udp.c6
2 files changed, 8 insertions, 4 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 031752efe1ab..456718921552 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1264,6 +1264,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
int peeked, off = 0;
int err;
int is_udplite = IS_UDPLITE(sk);
+ bool checksum_valid = false;
bool slow;
if (flags & MSG_ERRQUEUE)
@@ -1289,11 +1290,12 @@ 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 {
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 1173557ea551..7aa424c77445 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -399,6 +399,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
int peeked, off = 0;
int err;
int is_udplite = IS_UDPLITE(sk);
+ bool checksum_valid = false;
int is_udp4;
bool slow;
@@ -430,11 +431,12 @@ 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 {