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Date:   Thu, 6 Jun 2019 17:23:42 +0800
From:   Gen Zhang <blackgod016574@gmail.com>
To:     paul@paul-moore.com, sds@tycho.nsa.gov, eparis@parisplace.org
Cc:     selinux@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v3] selinux: lsm: fix a missing-check bug in
 selinux_add_mnt_opt( )
Message-ID: <20190606092342.GA21672@zhanggen-UX430UQ>
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User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
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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@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..4e4c1c6 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1052,15 +1052,23 @@ 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) {
+				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;
 }