linux-kernel - [PATCH] sctp: socket.c validate sprstat

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Message-Id: <20181027202026.32157-1-tomasbortoli@gmail.com>
Date:   Sat, 27 Oct 2018 22:20:26 +0200
From:   Tomas Bortoli <tomasbortoli@...il.com>
To:     vyasevich@...il.com, nhorman@...driver.com,
        marcelo.leitner@...il.com
Cc:     davem@...emloft.net, linux-sctp@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tomas Bortoli <tomasbortoli@...il.com>
Subject: [PATCH] sctp: socket.c validate sprstat_policy

It is possible to perform out-of-bound reads on
sctp_getsockopt_pr_streamstatus() and on
sctp_getsockopt_pr_assocstatus() by passing from userspace a
sprstat_policy that overflows the abandoned_sent/abandoned_unsent
fixed length arrays. The over-read data are directly copied/leaked
to userspace.

Signed-off-by: Tomas Bortoli <tomasbortoli@...il.com>
Reported-by: syzbot+5da0d0a72a9e7d791748@...kaller.appspotmail.com
---
v2 - added forgot ||

 net/sctp/socket.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index fc0386e8ff23..5290b8bd40c8 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -7083,7 +7083,8 @@ static int sctp_getsockopt_pr_assocstatus(struct sock *sk, int len,
 	}
 
 	policy = params.sprstat_policy;
-	if (!policy || (policy & ~(SCTP_PR_SCTP_MASK | SCTP_PR_SCTP_ALL)))
+	if (!policy || (policy & ~(SCTP_PR_SCTP_MASK | SCTP_PR_SCTP_ALL)) ||
+	    __SCTP_PR_INDEX(policy) > SCTP_PR_INDEX(MAX))
 		goto out;
 
 	asoc = sctp_id2assoc(sk, params.sprstat_assoc_id);
@@ -7142,7 +7143,8 @@ static int sctp_getsockopt_pr_streamstatus(struct sock *sk, int len,
 	}
 
 	policy = params.sprstat_policy;
-	if (!policy || (policy & ~(SCTP_PR_SCTP_MASK | SCTP_PR_SCTP_ALL)))
+	if (!policy || (policy & ~(SCTP_PR_SCTP_MASK | SCTP_PR_SCTP_ALL)) ||
+	    __SCTP_PR_INDEX(policy) > SCTP_PR_INDEX(MAX))
 		goto out;
 
 	asoc = sctp_id2assoc(sk, params.sprstat_assoc_id);
-- 
2.11.0