linux-kernel - [PATCH 5.16 002/126] selinux: fix double free of cond

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Message-Id: <20220207103804.140013578@linuxfoundation.org>
Date:   Mon,  7 Feb 2022 12:05:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vratislav Bendel <vbendel@...hat.com>,
        Paul Moore <paul@...l-moore.com>
Subject: [PATCH 5.16 002/126] selinux: fix double free of cond_list on error paths

From: Vratislav Bendel <vbendel@...hat.com>

commit 186edf7e368c40d06cf727a1ad14698ea67b74ad upstream.

On error path from cond_read_list() and duplicate_policydb_cond_list()
the cond_list_destroy() gets called a second time in caller functions,
resulting in NULL pointer deref.  Fix this by resetting the
cond_list_len to 0 in cond_list_destroy(), making subsequent calls a
noop.

Also consistently reset the cond_list pointer to NULL after freeing.

Cc: stable@...r.kernel.org
Signed-off-by: Vratislav Bendel <vbendel@...hat.com>
[PM: fix line lengths in the description]
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 security/selinux/ss/conditional.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -152,6 +152,8 @@ static void cond_list_destroy(struct pol
 	for (i = 0; i < p->cond_list_len; i++)
 		cond_node_destroy(&p->cond_list[i]);
 	kfree(p->cond_list);
+	p->cond_list = NULL;
+	p->cond_list_len = 0;
 }
 
 void cond_policydb_destroy(struct policydb *p)
@@ -441,7 +443,6 @@ int cond_read_list(struct policydb *p, v
 	return 0;
 err:
 	cond_list_destroy(p);
-	p->cond_list = NULL;
 	return rc;
 }