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Date:   Thu, 30 May 2019 16:54:38 +0800
From:   Gen Zhang <blackgod016574@gmail.com>
To:     Ondrej Mosnacek <omosnace@redhat.com>
Cc:     Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Eric Paris <eparis@parisplace.org>, ccross@android.com,
        selinux@vger.kernel.org,
        Linux kernel mailing list <linux-kernel@vger.kernel.org>,
        netdev@vger.kernel.org
Subject: [PATCH v2] hooks: fix a missing-check bug in selinux_add_mnt_opt()
Message-ID: <20190530085438.GA2862@zhanggen-UX430UQ>
References: <20190530080602.GA3600@zhanggen-UX430UQ>
 <CAFqZXNtX1R1VDFxm7Jco3BZ=pVnNiHU3-C=d8MhCVV1XSUQ8bw@mail.gmail.com>
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In selinux_add_mnt_opt(), 'val' is allcoted by kmemdup_nul(). It returns
NULL when fails. So 'val' should be checked.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
Fixes: 757cbe597fe8 ("LSM: new method: ->sb_add_mnt_opt()")
---
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3ec702c..4797c63 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1052,8 +1052,11 @@ static int selinux_add_mnt_opt(const char *option, const char *val, int len,
 	if (token == Opt_error)
 		return -EINVAL;
 
-	if (token != Opt_seclabel)
-		val = kmemdup_nul(val, len, GFP_KERNEL);
+	if (token != Opt_seclabel) {
+			val = kmemdup_nul(val, len, GFP_KERNEL);
+			if (!val)
+				return -ENOMEM;
+	}
 	rc = selinux_add_opt(token, val, mnt_opts);
 	if (unlikely(rc)) {
 		kfree(val);