[ 04/80] sctp: fix -ENOMEM result with invalid user space pointer in sendto() syscall

Greg Kroah-Hartman
2013-01-09T20:37:11Z

From: Tommi Rantala <tt.rantala@gmail.com>

[ Upstream commit 6e51fe7572590d8d86e93b547fab6693d305fd0d ]

Consider the following program, that sets the second argument to the
sendto() syscall incorrectly:

#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>

int main(void)
{
int fd;
struct sockaddr_in sa;

fd = socket(AF_INET, SOCK_STREAM, 132 /*IPPROTO_SCTP*/);
if (fd < 0)
return 1;

memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_addr.s_addr = inet_addr("127.0.0.1");
sa.sin_port = htons(11111);

sendto(fd, NULL, 1, 0, (struct sockaddr *)&sa, sizeof(sa));

return 0;
}

We get -ENOMEM:

$ strace -e sendto ./demo
sendto(3, NULL, 1, 0, {sa_family=AF_INET, sin_port=htons(11111), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 ENOMEM (Cannot allocate memory)

Propagate the error code from sctp_user_addto_chunk(), so that we will
tell user space what actually went wrong:

$ strace -e sendto ./demo
sendto(3, NULL, 1, 0, {sa_family=AF_INET, sin_port=htons(11111), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EFAULT (Bad address)

Noticed while running Trinity (the syscall fuzzer).

Signed-off-by: Tommi Rantala <tt.rantala@gmail.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/chunk.c | 13 +++++++++----
net/sctp/socket.c | 4 ++--
2 files changed, 11 insertions(+), 6 deletions(-)

--- a/net/sctp/chunk.c
+++ b/net/sctp/chunk.c
@@ -183,7 +183,7 @@ struct sctp_datamsg *sctp_datamsg_from_u

msg = sctp_datamsg_new(GFP_KERNEL);
if (!msg)
- return NULL;
+ return ERR_PTR(-ENOMEM);

/* Note: Calculate this outside of the loop, so that all fragments
* have the same expiration.
@@ -280,8 +280,11 @@ struct sctp_datamsg *sctp_datamsg_from_u

chunk = sctp_make_datafrag_empty(asoc, sinfo, len, frag, 0);

- if (!chunk)
+ if (!chunk) {
+ err = -ENOMEM;
goto errout;
+ }
+
err = sctp_user_addto_chunk(chunk, offset, len, msgh->msg_iov);
if (err < 0)
goto errout_chunk_free;
@@ -315,8 +318,10 @@ struct sctp_datamsg *sctp_datamsg_from_u

chunk = sctp_make_datafrag_empty(asoc, sinfo, over, frag, 0);

- if (!chunk)
+ if (!chunk) {
+ err = -ENOMEM;
goto errout;
+ }

err = sctp_user_addto_chunk(chunk, offset, over,msgh->msg_iov);

@@ -342,7 +347,7 @@ errout:
sctp_chunk_free(chunk);
}
sctp_datamsg_put(msg);
- return NULL;
+ return ERR_PTR(err);
}

/* Check whether this message has expired. */
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1908,8 +1908,8 @@ SCTP_STATIC int sctp_sendmsg(struct kioc

/* Break the message into multiple chunks of maximum size. */
datamsg = sctp_datamsg_from_user(asoc, sinfo, msg, msg_len);
- if (!datamsg) {
- err = -ENOMEM;
+ if (IS_ERR(datamsg)) {
+ err = PTR_ERR(datamsg);
goto out_free;
}