[PATCH net] sctp: walk the list of asoc safely

[Greg Kroah-Hartman]

In sctp_sendmesg(), when walking the list of endpoint associations, the
association can be dropped from the list, making the list corrupt.
Properly handle this by using list_for_each_entry_safe()

Fixes: 4910280503f3 ("sctp: add support for snd flag SCTP_SENDALL process in 
sendmsg")
Reported-by: Secunia Research <v...@secunia.com>
Tested-by: Secunia Research <v...@secunia.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index f93c3cf9e567..65d6d04546ae 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2027,7 +2027,7 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr 
*msg, size_t msg_len)
        struct sctp_endpoint *ep = sctp_sk(sk)->ep;
        struct sctp_transport *transport = NULL;
        struct sctp_sndrcvinfo _sinfo, *sinfo;
-       struct sctp_association *asoc;
+       struct sctp_association *asoc, *tmp;
        struct sctp_cmsgs cmsgs;
        union sctp_addr *daddr;
        bool new = false;
@@ -2053,7 +2053,7 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr 
*msg, size_t msg_len)
 
        /* SCTP_SENDALL process */
        if ((sflags & SCTP_SENDALL) && sctp_style(sk, UDP)) {
-               list_for_each_entry(asoc, &ep->asocs, asocs) {
+               list_for_each_entry_safe(asoc, tmp, &ep->asocs, asocs) {
                        err = sctp_sendmsg_check_sflags(asoc, sflags, msg,
                                                        msg_len);
                        if (err == 0)