linux-kernel - [PATCH AUTOSEL 5.6 154/606] apparmor: fix potential label refcnt leak in aa_change

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Date:   Mon,  8 Jun 2020 19:04:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>,
        John Johansen <john.johansen@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-security-module@...r.kernel.org
Subject: [PATCH AUTOSEL 5.6 154/606] apparmor: fix potential label refcnt leak in aa_change_profile

From: Xiyu Yang <xiyuyang19@...an.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@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
Signed-off-by: John Johansen <john.johansen@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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