netdev - [PATCH net] sctp: prevent info leak in sctp_make

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Message-ID: <YNrXoNAiQama8Us8@mwanda>
Date:   Tue, 29 Jun 2021 11:19:44 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Vlad Yasevich <vyasevich@...il.com>,
        Xin Long <lucien.xin@...il.com>
Cc:     Neil Horman <nhorman@...driver.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-sctp@...r.kernel.org,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH net] sctp: prevent info leak in sctp_make_heartbeat()

The "hbinfo" struct has a 4 byte hole at the end so we have to zero it
out to prevent stack information from being disclosed.

Fixes: fe59379b9ab7 ("sctp: do the basic send and recv for PLPMTUD probe")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
Btw = {} is the newest way to initialize holes.

In the past we have debated whether = {} will *always* zero out struct
holes and it wasn't clear from the C standard.  But it turns out that
"= {}" is not part of the standard but is instead a GCC extension and it
does clear the holes.  In GCC (not the C standard) then = {0}; is also
supposed to initialize holes in there was a bug in one version where it
didn't.

So that's nice, because adding memset()s to zero everywhere was ugly.

 net/sctp/sm_make_chunk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 587fb3cb88e2..3a290f620e96 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1162,7 +1162,7 @@ struct sctp_chunk *sctp_make_new_encap_port(const struct sctp_association *asoc,
 struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *asoc,
 				       const struct sctp_transport *transport)
 {
-	struct sctp_sender_hb_info hbinfo;
+	struct sctp_sender_hb_info hbinfo = {};
 	struct sctp_chunk *retval;
 
 	retval = sctp_make_control(asoc, SCTP_CID_HEARTBEAT, 0,
-- 
2.30.2