linux-kernel - [PATCH] sctp: fix a potential buffer overflow in sctp_sched_set

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Date:   Tue, 2 May 2023 08:26:30 +0000
From:   Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
To:     Neil Horman <nhorman@...driver.com>
CC:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>
Subject: [PATCH] sctp: fix a potential buffer overflow in
 sctp_sched_set_sched()

The 'sched' index value must be checked before accessing an element
of the 'sctp_sched_ops' array. Otherwise, it can lead to buffer overflow.

Note that it's harmless since the 'sched' parameter is checked before
calling 'sctp_sched_set_sched'.

Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with SVACE.

Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
Signed-off-by: Ilia.Gavrilov <Ilia.Gavrilov@...otecs.ru>
---
 net/sctp/stream_sched.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/sctp/stream_sched.c b/net/sctp/stream_sched.c
index 330067002deb..a339917d7197 100644
--- a/net/sctp/stream_sched.c
+++ b/net/sctp/stream_sched.c
@@ -146,18 +146,19 @@ static void sctp_sched_free_sched(struct sctp_stream *stream)
 int sctp_sched_set_sched(struct sctp_association *asoc,
 			 enum sctp_sched_type sched)
 {
-	struct sctp_sched_ops *n = sctp_sched_ops[sched];
+	struct sctp_sched_ops *n;
 	struct sctp_sched_ops *old = asoc->outqueue.sched;
 	struct sctp_datamsg *msg = NULL;
 	struct sctp_chunk *ch;
 	int i, ret = 0;
 
-	if (old == n)
-		return ret;
-
 	if (sched > SCTP_SS_MAX)
 		return -EINVAL;
 
+	n = sctp_sched_ops[sched];
+	if (old == n)
+		return ret;
+
 	if (old)
 		sctp_sched_free_sched(&asoc->stream);
 
-- 
2.30.2