[PATCH 5.4 068/111] apparmor: Fix aa_label refcnt leak in policy_update

[Greg Kroah-Hartman]

From: Xiyu Yang <xiyuyan...@fudan.edu.cn>

commit c6b39f070722ea9963ffe756bfe94e89218c5e63 upstream.

policy_update() invokes begin_current_label_crit_section(), which
returns a reference of the updated aa_label object to "label" with
increased refcount.

When policy_update() returns, "label" becomes invalid, so the refcount
should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
policy_update(). When aa_may_manage_policy() returns not NULL, the
refcnt increased by begin_current_label_crit_section() is not decreased,
causing a refcnt leak.

Fix this issue by jumping to "end_section" label when
aa_may_manage_policy() returns not NULL.

Fixes: 5ac8c355ae00 ("apparmor: allow introspecting the loaded policy pre 
internal transform")
Signed-off-by: Xiyu Yang <xiyuyan...@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin....@gmail.com>
Signed-off-by: John Johansen <john.johan...@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 security/apparmor/apparmorfs.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -424,7 +424,7 @@ static ssize_t policy_update(u32 mask, c
         */
        error = aa_may_manage_policy(label, ns, mask);
        if (error)
-               return error;
+               goto end_section;
 
        data = aa_simple_write_to_buffer(buf, size, size, pos);
        error = PTR_ERR(data);
@@ -432,6 +432,7 @@ static ssize_t policy_update(u32 mask, c
                error = aa_replace_profiles(ns, label, mask, data);
                aa_put_loaddata(data);
        }
+end_section:
        end_current_label_crit_section(label);
 
        return error;