sock: fix sendmmsg for partial sendmsg
authorSoheil Hassas Yeganeh <soheil@google.com>
Fri, 4 Nov 2016 19:36:49 +0000 (15:36 -0400)
committerBen Hutchings <ben@decadent.org.uk>
Thu, 16 Mar 2017 02:18:54 +0000 (02:18 +0000)
commit058627c4b45f3d3b34925cf1217c7e519967fad6
tree34f4a03af48e335b683e84fc325bd929d934f872
parentd1e281084e5cc94fddfaa2d769b7c5401f915aa5
sock: fix sendmmsg for partial sendmsg

[ Upstream commit 3023898b7d4aac65987bd2f485cc22390aae6f78 ]

Do not send the next message in sendmmsg for partial sendmsg
invocations.

sendmmsg assumes that it can continue sending the next message
when the return value of the individual sendmsg invocations
is positive. It results in corrupting the data for TCP,
SCTP, and UNIX streams.

For example, sendmmsg([["abcd"], ["efgh"]]) can result in a stream
of "aefgh" if the first sendmsg invocation sends only the first
byte while the second sendmsg goes through.

Datagram sockets either send the entire datagram or fail, so
this patch affects only sockets of type SOCK_STREAM and
SOCK_SEQPACKET.

Fixes: 228e548e6020 ("net: Add sendmmsg socket system call")
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Maciej ┼╗enczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: we don't have the iov_iter API, so make
 ___sys_sendmsg() calculate and write back the remaining length]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
net/socket.c