apparmor: fix potential label refcnt leak in aa_change_profile

aa_change_profile() invokes aa_get_current_label(), which returns
a reference of the current task's label.

According to the comment of aa_get_current_label(), the returned
reference must be put with aa_put_label().
However, when the original object pointed by "label" becomes
unreachable because aa_change_profile() returns or a new object
is assigned to "label", reference count increased by
aa_get_current_label() is not decreased, causing a refcnt leak.

Fix this by calling aa_put_label() before aa_change_profile() return
and dropping unnecessary aa_get_current_label().

Fixes: 553cea0d6b39 ("apparmor: update domain transitions that are subsets of confinement at nnp")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index 6ceb74e0f7895548c5faaa6f95b7eb8c11367e87..a84ef030fbd7d18c0d6825ba8f07e89b241a98a9 100644 (file)
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -1328,6 +1328,7 @@ int aa_change_profile(const char *fqname, int flags)
                ctx->nnp = aa_get_label(label);
 
        if (!fqname || !*fqname) {
+               aa_put_label(label);
                AA_DEBUG("no profile name");
                return -EINVAL;
        }
@@ -1346,8 +1347,6 @@ int aa_change_profile(const char *fqname, int flags)
                        op = OP_CHANGE_PROFILE;
        }
 
-       label = aa_get_current_label();
-
        if (*fqname == '&') {
                stack = true;
                /* don't have label_parse() do stacking */