linux-kernel - [PATCH 5.1 018/115] selinux: fix a missing-check bug in selinux_add_mnt

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Message-Id: <20190617210800.846376843@linuxfoundation.org>
Date:   Mon, 17 Jun 2019 23:08:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Gen Zhang <blackgod016574@...il.com>,
        Paul Moore <paul@...l-moore.com>
Subject: [PATCH 5.1 018/115] selinux: fix a missing-check bug in selinux_add_mnt_opt( )

From: Gen Zhang <blackgod016574@...il.com>

commit e2e0e09758a6f7597de0f9b819647addfb71b6bd upstream.

In selinux_add_mnt_opt(), 'val' is allocated by kmemdup_nul(). It returns
NULL when fails. So 'val' should be checked. And 'mnt_opts' should be
freed when error.

Signed-off-by: Gen Zhang <blackgod016574@...il.com>
Fixes: 757cbe597fe8 ("LSM: new method: ->sb_add_mnt_opt()")
Cc: <stable@...r.kernel.org>
[PM: fixed some indenting problems]
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/selinux/hooks.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1048,15 +1048,24 @@ static int selinux_add_mnt_opt(const cha
 	if (token == Opt_error)
 		return -EINVAL;
 
-	if (token != Opt_seclabel)
+	if (token != Opt_seclabel) {
 		val = kmemdup_nul(val, len, GFP_KERNEL);
+		if (!val) {
+			rc = -ENOMEM;
+			goto free_opt;
+		}
+	}
 	rc = selinux_add_opt(token, val, mnt_opts);
 	if (unlikely(rc)) {
 		kfree(val);
-		if (*mnt_opts) {
-			selinux_free_mnt_opts(*mnt_opts);
-			*mnt_opts = NULL;
-		}
+		goto free_opt;
+	}
+	return rc;
+
+free_opt:
+	if (*mnt_opts) {
+		selinux_free_mnt_opts(*mnt_opts);
+		*mnt_opts = NULL;
 	}
 	return rc;
 }