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Subject[PATCH v3] selinux: fix another double free
Date
From: Tom Rix <trix@redhat.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
earlier nodes.

Because cond_read_node no longer does any error handling, the goto's
the error case are redundant. Instead just return the error code.

Fixes: 60abd3181db2 ("selinux: convert cond_list to array")

Signed-off-by: Tom Rix <trix@redhat.com>
---
v3: simplify returns

security/selinux/ss/conditional.c | 18 +++++-------------
1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index da94a1b4bfda..450bc02f4cd2 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -392,27 +392,19 @@ static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)

rc = next_entry(buf, fp, sizeof(u32) * 2);
if (rc)
- goto err;
+ return rc;

expr->expr_type = le32_to_cpu(buf[0]);
expr->bool = le32_to_cpu(buf[1]);

- if (!expr_node_isvalid(p, expr)) {
- rc = -EINVAL;
- goto err;
- }
+ if (!expr_node_isvalid(p, expr))
+ return -EINVAL;
}

rc = cond_read_av_list(p, fp, &node->true_list, NULL);
if (rc)
- goto err;
- rc = cond_read_av_list(p, fp, &node->false_list, &node->true_list);
- if (rc)
- goto err;
- return 0;
-err:
- cond_node_destroy(node);
- return rc;
+ return rc;
+ return cond_read_av_list(p, fp, &node->false_list, &node->true_list);
}

int cond_read_list(struct policydb *p, void *fp)
--
2.18.1
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