apparmor: fix reference count leak in aa_pivotroot()

commit 5ee978fdbd011d71f07a9aa93eff21c6f228a41b upstream.

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: 559bef1f8ff1 ("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>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
index 7c8e6d748306216e30112feb73ee34749fb70212..4b433cf1526fc5ac78ca4d37c20b49bb6693dab1 100644 (file)
--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -683,6 +683,7 @@ 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);