[PATCH 4.19 273/313] sctp: walk the list of asoc safely

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

[ Upstream commit ba59fb0273076637f0add4311faa990a5eec27c0 ]

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 <vuln@xxxxxxxxxxx>
Tested-by: Secunia Research <vuln@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/sctp/socket.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2045,7 +2045,7 @@ static int sctp_sendmsg(struct sock *sk,
 	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;
@@ -2071,7 +2071,7 @@ static int sctp_sendmsg(struct sock *sk,
 
 	/* 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)