linux-kernel - [PATCH] selinux: fix another double free

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Message-Id: <20200611155830.8941-1-trix@redhat.com>
Date:   Thu, 11 Jun 2020 08:58:30 -0700
From:   trix@...hat.com
To:     paul@...l-moore.com, stephen.smalley.work@...il.com,
        eparis@...isplace.org, omosnace@...hat.com, weiyongjun1@...wei.com
Cc:     selinux@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] selinux: fix another double free

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

Clang static analysis reports this double free error

security/selinux/ss/conditional.c:139:2: warning: Attempt to free released memory [unix.Malloc]
        kfree(node->expr.nodes);
        ^~~~~~~~~~~~~~~~~~~~~~~

When cond_read_node fails, it calls cond_node_destroy which frees the
node but does not poison the entry in the node list.  So when it
returns to its caller cond_read_list, cond_read_list deletes the
partial list.  The latest entry in the list will be deleted twice.

So instead of freeing the node in cond_read_node, let list freeing in
code_read_list handle the freeing the problem node along with all of the the
earlier nodes.

Signed-off-by: Tom Rix <trix@...hat.com>
---
 security/selinux/ss/conditional.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index da94a1b4bfda..ffb31af22f4f 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -411,7 +411,6 @@ static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
 		goto err;
 	return 0;
 err:
-	cond_node_destroy(node);
 	return rc;
 }
 
-- 
2.18.1