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Date:   Thu, 6 Jun 2019 16:55:24 +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 v4] selinux: lsm: fix a missing-check bug in
 selinux_sb_eat_lsm_o pts()
Message-ID: <20190606085524.GA21119@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_sb_eat_lsm_opts(), 'arg' is allocated by kmemdup_nul(). It
returns NULL when fails. So 'arg' should be checked. And 'mnt_opts' 
should be freed when error.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
Fixes: 99dbbb593fe6 ("selinux: rewrite selinux_sb_eat_lsm_opts()")
---
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3ec702c..13479cd 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2616,10 +2616,11 @@ static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts)
 	char *from = options;
 	char *to = options;
 	bool first = true;
+	int rc;
 
 	while (1) {
 		int len = opt_len(from);
-		int token, rc;
+		int token;
 		char *arg = NULL;
 
 		token = match_opt_prefix(from, len, &arg);
@@ -2635,15 +2636,15 @@ static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts)
 						*q++ = c;
 				}
 				arg = kmemdup_nul(arg, q - arg, GFP_KERNEL);
+				if (!arg) {
+					rc = -ENOMEM;
+					goto free_opt;
+				}
 			}
 			rc = selinux_add_opt(token, arg, mnt_opts);
 			if (unlikely(rc)) {
 				kfree(arg);
-				if (*mnt_opts) {
-					selinux_free_mnt_opts(*mnt_opts);
-					*mnt_opts = NULL;
-				}
-				return rc;
+				goto free_opt;
 			}
 		} else {
 			if (!first) {	// copy with preceding comma
@@ -2661,6 +2662,12 @@ static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts)
 	}
 	*to = '\0';
 	return 0;
+free_opt:
+	if (*mnt_opts) {
+		selinux_free_mnt_opts(*mnt_opts);
+		*mnt_opts = NULL;
+	}
+	return rc;
 }
 
 static int selinux_sb_remount(struct super_block *sb, void *mnt_opts)