diff options
| author | Eric Dumazet <edumazet@google.com> | 2015-12-30 08:51:12 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-01-04 17:23:36 -0500 |
| commit | 197c949e7798fbf28cfadc69d9ca0c2abbf93191 (patch) | |
| tree | b11734b5208854fbbbdcbcdb02a994e03c87d0c9 /net/ipv4 | |
| parent | 815bc580fe4ebffc35cc837a775f5400f5a607c4 (diff) | |
udp: properly support MSG_PEEK with truncated buffers
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>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/udp.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 8841e984f8bf..ac14ae44390d 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1271,6 +1271,7 @@ 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) @@ -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 { |