[PATCH iproute2] libnetlink: fix leak and using unused memory on error

[Stephen Hemminger]

If an error happens in multi-segment message (tc only)
then report the error and stop processing further responses.
This also fixes refering to the buffer after free.

The sequence check is not necessary here because the
response message has already been validated to be in
the window of the sequence number of the iov.

Reported-by: Mahesh Bandewar <mah...@bandewar.net>
Fixes: 7b2ee50c0cd5 ("hv_netvsc: common detach logic")
Signed-off-by: Stephen Hemminger <step...@networkplumber.org>
---
 lib/libnetlink.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 928de1dd16d8..586809292594 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -617,7 +617,6 @@ static int __rtnl_talk_iov(struct rtnl_handle *rtnl, struct 
iovec *iov,
        msg.msg_iovlen = 1;
        i = 0;
        while (1) {
-next:
                status = rtnl_recvmsg(rtnl->fd, &msg, &buf);
                ++i;
 
@@ -660,27 +659,23 @@ next:
 
                                if (l < sizeof(struct nlmsgerr)) {
                                        fprintf(stderr, "ERROR truncated\n");
-                               } else if (!err->error) {
+                                       free(buf);
+                                       return -1;
+                               }
+
+                               if (!err->error)
                                        /* check messages from kernel */
                                        nl_dump_ext_ack(h, errfn);
 
-                                       if (answer)
-                                               *answer = (struct nlmsghdr 
*)buf;
-                                       else
-                                               free(buf);
-                                       if (h->nlmsg_seq == seq)
-                                               return 0;
-                                       else if (i < iovlen)
-                                               goto next;
-                                       return 0;
-                               }
-
                                if (rtnl->proto != NETLINK_SOCK_DIAG &&
                                    show_rtnl_err)
                                        rtnl_talk_error(h, err, errfn);
 
                                errno = -err->error;
-                               free(buf);
+                               if (answer)
+                                       *answer = (struct nlmsghdr *)buf;
+                               else
+                                       free(buf);
                                return -i;
                        }
 
-- 
2.18.0