[PATCH AUTOSEL 5.6 154/606] apparmor: fix potential label refcnt leak in aa_change_profile

Sasha Levin
2020-06-09T00:32:18Z

From: Xiyu Yang <xiyuyang19@fudan.edu.cn>

commit a0b845ffa0d91855532b50fc040aeb2d8338dca4 upstream.

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: 9fcf78cca198 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
security/apparmor/domain.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index 6ceb74e0f789..a84ef030fbd7 100644
--- 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 */
--
2.25.1