[net,v4] sctp: fix a potential OOB access in sctp_sched_set_sched()

Commit Message

Gavrilov Ilia May 3, 2023, 1:37 p.m. UTC

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

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.

Reviewed-by: Xin Long <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Signed-off-by: Ilia.Gavrilov <[e-mail]>
---
V2:
 - Change the order of local variables 
 - Specify the target tree in the subject
V3:
 - Change description
 - Remove 'fixes'
V4:
 - revert to V2
 net/sctp/stream_sched.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Comments

Marcelo Ricardo Leitner May 3, 2023, 1:44 p.m. UTC | #1

On Wed, May 03, 2023 at 01:37:59PM +0000, Gavrilov Ilia wrote:
> The 'sched' index value must be checked before accessing an element
> of the 'sctp_sched_ops' array. Otherwise, it can lead to OOB access.
> 
> 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.
> 
> Reviewed-by: Xin Long <[e-mail]>
> Reviewed-by: Simon Horman <[e-mail]>
> Signed-off-by: Ilia.Gavrilov <[e-mail]>

Acked-by: Marcelo Ricardo Leitner <[e-mail]>

Thx!

Jakub Kicinski May 4, 2023, 1:49 a.m. UTC | #2

On Wed, 3 May 2023 13:37:59 +0000 Gavrilov Ilia wrote:
> The 'sched' index value must be checked before accessing an element
> of the 'sctp_sched_ops' array. Otherwise, it can lead to OOB access.
> 
> Note that it's harmless since the 'sched' parameter is checked before
> calling 'sctp_sched_set_sched'.

Not a fix, so it needs to wait for net-next to open, see below.
When you repost please do so separately, not in the existing thread.

## Form letter - net-next-closed

The merge window for v6.3 has begun and therefore net-next is closed
for new drivers, features, code refactoring and optimizations.
We are currently accepting bug fixes only.

Please repost when net-next reopens after May 8th.

RFC patches sent for review only are obviously welcome at any time.

See: https://www.kernel.org/doc/html/next/process/maintainer-netdev.html#development-cycle

Patch

diff --git a/net/sctp/stream_sched.c b/net/sctp/stream_sched.c
index 330067002deb..4d076a9b8592 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 *old = asoc->outqueue.sched;
 	struct sctp_datamsg *msg = NULL;
+	struct sctp_sched_ops *n;
 	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);