linux-kernel - [PATCH] lsm:fix a missing-check bug in smack_sb_eat_lsm

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Message-Id: <20210416095303.530-1-hbut_tan@163.com>
Date:   Fri, 16 Apr 2021 17:53:03 +0800
From:    Zhongjun Tan <hbut_tan@....com>
To:     casey@...aufler-ca.com, jmorris@...ei.org, serge@...lyn.com
Cc:     linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, Zhongjun Tan <tanzhongjun@...ong.com>
Subject: [PATCH] lsm:fix a missing-check bug in smack_sb_eat_lsm_opts()

From: Zhongjun Tan <tanzhongjun@...ong.com>

In smack_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: Zhongjun Tan <tanzhongjun@...ong.com>
---
 security/smack/smack_lsm.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 223a6da..0d5439f 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -696,10 +696,11 @@ static int smack_sb_eat_lsm_opts(char *options, void **mnt_opts)
 {
 	char *from = options, *to = options;
 	bool first = true;
+	int rc;
 
 	while (1) {
 		char *next = strchr(from, ',');
-		int token, len, rc;
+		int token, len;
 		char *arg = NULL;
 
 		if (next)
@@ -710,13 +711,14 @@ static int smack_sb_eat_lsm_opts(char *options, void **mnt_opts)
 		token = match_opt_prefix(from, len, &arg);
 		if (token != Opt_error) {
 			arg = kmemdup_nul(arg, from + len - arg, GFP_KERNEL);
+			if (!arg) {
+				rc = -ENOMEM;
+				goto free_mnt_opts;
 			rc = smack_add_opt(token, arg, mnt_opts);
+			}
 			if (unlikely(rc)) {
 				kfree(arg);
-				if (*mnt_opts)
-					smack_free_mnt_opts(*mnt_opts);
-				*mnt_opts = NULL;
-				return rc;
+				goto free_mnt_opts;
 			}
 		} else {
 			if (!first) {	// copy with preceding comma
@@ -734,6 +736,13 @@ static int smack_sb_eat_lsm_opts(char *options, void **mnt_opts)
 	}
 	*to = '\0';
 	return 0;
+
+free_mnt_opts:
+	if (*mnt_opts) {
+		smack_free_mnt_opts(*mnt_opts);
+		*mnt_opts = NULL;
+	}
+	return rc;
 }
 
 /**
-- 
1.9.1