Commit aa449a79 authored Jun 15, 2020 by Tom Rix Committed by Paul Moore Jun 16, 2020

selinux: fix a double free in cond_read_node()/cond_read_list()



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.

Cc: stable@vger.kernel.org
Fixes: 60abd318 ("selinux: convert cond_list to array")
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
[PM: subject line tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>

parent 65de5096

security/selinux/ss/conditional.c

+5 −13

Original line number	Diff line number	Diff line
		@@ -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 cond_read_av_list(p, fp, &node->false_list, &node->true_list);
		}

		int cond_read_list(struct policydb p, void fp)

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