linux-kernel - [PATCH 4.19 177/206] selinux: fix double free

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Message-Id: <20200623195325.745737040@linuxfoundation.org>
Date:   Tue, 23 Jun 2020 21:58:25 +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, Tom Rix <trix@...hat.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Paul Moore <paul@...l-moore.com>
Subject: [PATCH 4.19 177/206] selinux: fix double free

From: Tom Rix <trix@...hat.com>

commit 65de50969a77509452ae590e9449b70a22b923bb upstream.

Clang's static analysis tool reports these double free memory errors.

security/selinux/ss/services.c:2987:4: warning: Attempt to free released memory [unix.Malloc]
                        kfree(bnames[i]);
                        ^~~~~~~~~~~~~~~~
security/selinux/ss/services.c:2990:2: warning: Attempt to free released memory [unix.Malloc]
        kfree(bvalues);
        ^~~~~~~~~~~~~~

So improve the security_get_bools error handling by freeing these variables
and setting their return pointers to NULL and the return len to 0

Cc: stable@...r.kernel.org
Signed-off-by: Tom Rix <trix@...hat.com>
Acked-by: Stephen Smalley <stephen.smalley.work@...il.com>
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/selinux/ss/services.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2857,8 +2857,12 @@ err:
 	if (*names) {
 		for (i = 0; i < *len; i++)
 			kfree((*names)[i]);
+		kfree(*names);
 	}
 	kfree(*values);
+	*len = 0;
+	*names = NULL;
+	*values = NULL;
 	goto out;
 }