linux-kernel - [PATCH 5.2 180/215] selinux: check sidtab limit before adding a new entry

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Message-Id: <20190729190811.251798429@linuxfoundation.org>
Date:   Mon, 29 Jul 2019 21:22:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ondrej Mosnacek <omosnace@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Moore <paul@...l-moore.com>
Subject: [PATCH 5.2 180/215] selinux: check sidtab limit before adding a new entry

From: Ondrej Mosnacek <omosnace@...hat.com>

commit acbc372e6109c803cbee4733769d02008381740f upstream.

We need to error out when trying to add an entry above SIDTAB_MAX in
sidtab_reverse_lookup() to avoid overflow on the odd chance that this
happens.

Cc: stable@...r.kernel.org
Fixes: ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve performance")
Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/selinux/ss/sidtab.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/security/selinux/ss/sidtab.c
+++ b/security/selinux/ss/sidtab.c
@@ -286,6 +286,11 @@ static int sidtab_reverse_lookup(struct
 		++count;
 	}
 
+	/* bail out if we already reached max entries */
+	rc = -EOVERFLOW;
+	if (count >= SIDTAB_MAX)
+		goto out_unlock;
+
 	/* insert context into new entry */
 	rc = -ENOMEM;
 	dst = sidtab_do_lookup(s, count, 1);