[PATCH] lsm:fix a missing-check bug in smack_sb_eat_lsm_opts()

[Zhongjun Tan]

From: Zhongjun Tan <tanzhong...@yulong.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 <tanzhong...@yulong.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