[PATCH] apparmor: fix reference count leak in aa_pivotroot()

From: Xin Xiong <xiongx18@fudan.edu.cn>
To: John Johansen <john.johansen@canonical.com>,
	James Morris <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Seth Arnold <seth.arnold@canonical.com>,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: yuanxzhang@fudan.edu.cn, Xin Xiong <xiongx18@fudan.edu.cn>,
	Xiyu Yang <xiyuyang19@fudan.edu.cn>,
	Xin Tan <tanxin.ctf@gmail.com>
Subject: [PATCH] apparmor: fix reference count leak in aa_pivotroot()
Date: Thu, 28 Apr 2022 11:39:08 +0800	[thread overview]
Message-ID: <20220428033907.1658-1-xiongx18@fudan.edu.cn> (raw)

The aa_pivotroot() function has a reference counting bug in a specific
path. When aa_replace_current_label() returns on success, the function
forgets to decrement the reference count of “target”, which is
increased earlier by build_pivotroot(), causing a reference leak.

Fix it by decreasing the refcount of “target” in that path.

Fixes: 2ea3ffb7782a ("apparmor: add mount mediation")
Co-developed-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Co-developed-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
---
 security/apparmor/mount.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
index aa6fcfde3051..d0b19ab9137d 100644
--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -718,6 +718,7 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 			aa_put_label(target);
 			goto out;
 		}
+		aa_put_label(target);
 	} else
 		/* already audited error */
 		error = PTR_ERR(target);
-- 
2.25.1

