Re: [PATCH] sctp: avoid NULL pointer dereference in sctp_sf_violation
From: Xin Long <lucien.xin@gmail.com>
Date: 2021-11-03 12:44:02
Also in:
linux-sctp, lkml
On Tue, Nov 2, 2021 at 4:27 PM Alexey Khoroshilov [off-list ref] wrote:
Some callers (e.g. sctp_sf_violation_chunk) passes NULL to asoc argument of sctp_sf_violation. So, it should check it before calling sctp_vtag_verify(). Probably it could be exploited by a malicious SCTP packet to cause NULL pointer dereference.
I don't think asoc can be NULL in here, did you see any call trace caused by it? If this was found by a tool, please remove the unnecessary call from sctp_sf_violation_chunk() instead:
@@ -4893,9 +4893,6 @@ static enum sctp_disposition sctp_sf_violation_chunk( { static const char err_str[] = "The following chunk violates protocol:"; - if (!asoc) - return sctp_sf_violation(net, ep, asoc, type, arg, commands); -
Thanks.
quoted hunk ↗ jump to hunk
Found by Linux Verification Center (linuxtesting.org) with SVACE. Signed-off-by: Alexey Khoroshilov <redacted> Fixes: aa0f697e4528 ("sctp: add vtag check in sctp_sf_violation") --- net/sctp/sm_statefuns.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index fb3da4d8f4a3..77f3cd6c516e 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c@@ -4669,7 +4669,7 @@ enum sctp_disposition sctp_sf_violation(struct net *net, { struct sctp_chunk *chunk = arg; - if (!sctp_vtag_verify(chunk, asoc)) + if (asoc && !sctp_vtag_verify(chunk, asoc)) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); /* Make sure that the chunk has a valid length. */ --2.7.4