[patch] Smack: freeing an error pointer in smk_write_revoke_subj()

Dan Carpenter
2015-06-11T08:51:16Z

This code used to rely on the fact that kfree(NULL) was a no-op, but
then we changed smk_parse_smack() to return error pointers on failure
instead of NULL. Calling kfree() on an error pointer will oops.

I have re-arranged things a bit so that we only free things if they
have been allocated.

Fixes: e774ad683f42 ('smack: pass error code through pointers')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 6beac42..2716d02 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -2253,8 +2253,8 @@ static const struct file_operations smk_access2_ops = {
static ssize_t smk_write_revoke_subj(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
- char *data = NULL;
- const char *cp = NULL;
+ char *data;
+ const char *cp;
struct smack_known *skp;
struct smack_rule *sp;
struct list_head *rule_list;
@@ -2276,18 +2276,18 @@ static ssize_t smk_write_revoke_subj(struct file *file, const char __user *buf,

if (copy_from_user(data, buf, count) != 0) {
rc = -EFAULT;
- goto free_out;
+ goto out_data;
}

cp = smk_parse_smack(data, count);
if (IS_ERR(cp)) {
rc = PTR_ERR(cp);
- goto free_out;
+ goto out_data;
}

skp = smk_find_entry(cp);
if (skp = NULL)
- goto free_out;
+ goto out_cp;

rule_list = &skp->smk_rules;
rule_lock = &skp->smk_rules_lock;
@@ -2299,9 +2299,11 @@ static ssize_t smk_write_revoke_subj(struct file *file, const char __user *buf,

mutex_unlock(rule_lock);

-free_out:
- kfree(data);
+out_cp:
kfree(cp);
+out_data:
+ kfree(data);
+
return rc;
}