net/sctp: fix a null dereference in sctp_disposition sctp_sf_do_5_1D_ce()

[PATCH] net/sctp: fix a null dereference in sctp_disposition sctp_sf_do_5_1D_ce()

Posted by Alexandr Sapozhnkiov 2 months, 2 weeks ago

From: Alexandr Sapozhnikov <alsp705@gmail.com>

If new_asoc->peer.adaptation_ind=0 and sctp_ulpevent_make_authkey=0 
and sctp_ulpevent_make_authkey() returns 0, then the variable 
ai_ev remains zero and the zero will be dereferenced 
in the sctp_ulpevent_free() function.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Alexandr Sapozhnikov <alsp705@gmail.com>
---
 net/sctp/sm_statefuns.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 5adf0c0a6c1a..056544e1ca15 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -885,7 +885,8 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,
 	return SCTP_DISPOSITION_CONSUME;
 
 nomem_authev:
-	sctp_ulpevent_free(ai_ev);
+	if (ai_ev)
+		sctp_ulpevent_free(ai_ev);
 nomem_aiev:
 	sctp_ulpevent_free(ev);
 nomem_ev:
-- 
2.43.0

Re: [PATCH] net/sctp: fix a null dereference in sctp_disposition sctp_sf_do_5_1D_ce()

Posted by Markus Elfring 2 months, 2 weeks ago

…
> and sctp_ulpevent_make_authkey() returns 0, then the variable 
> ai_ev remains zero and the zero will be dereferenced 
> in the sctp_ulpevent_free() function.
…

Would a corresponding imperative wording become helpful for an improved change description?
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.17#n94

Regards,
Markus

Re: [PATCH] net/sctp: fix a null dereference in sctp_disposition sctp_sf_do_5_1D_ce()

Posted by Xin Long 2 months, 2 weeks ago

On Thu, Oct 2, 2025 at 5:14 AM Alexandr Sapozhnkiov <alsp705@gmail.com> wrote:
>
> From: Alexandr Sapozhnikov <alsp705@gmail.com>
>
> If new_asoc->peer.adaptation_ind=0 and sctp_ulpevent_make_authkey=0
> and sctp_ulpevent_make_authkey() returns 0, then the variable
> ai_ev remains zero and the zero will be dereferenced
> in the sctp_ulpevent_free() function.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Signed-off-by: Alexandr Sapozhnikov <alsp705@gmail.com>

Fixes: 30f6ebf65bc4 ("sctp: add SCTP_AUTH_NO_AUTH type for
AUTHENTICATION_EVENT")

Acked-by: Xin Long <lucien.xin@gmail.com>

Re: [PATCH] net/sctp: fix a null dereference in sctp_disposition sctp_sf_do_5_1D_ce()

Posted by Markus Elfring 2 months, 2 weeks ago

…
> > and sctp_ulpevent_make_authkey() returns 0, then the variable
> > ai_ev remains zero and the zero will be dereferenced
> > in the sctp_ulpevent_free() function.
…
> Fixes: 30f6ebf65bc4 ("sctp: add SCTP_AUTH_NO_AUTH type for
> AUTHENTICATION_EVENT")
…

See also:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.17#n145

Regards,
Markus