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LSM: SafeSetID: refactor policy parsing 

In preparation for changing the policy parsing logic, refactor the line
parsing logic to be less verbose and move it into a separate function.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>
This commit is contained in:
Jann Horn 2019-04-10 09:55:48 -07:00 committed by Micah Morton
parent 8068866c4a
commit 78ae7df96d
1 changed files with 33 additions and 51 deletions
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84
security/safesetid/securityfs.c
View File

@ -33,68 +33,50 @@ static struct safesetid_file_entry safesetid_files[] = {
/*
* In the case the input buffer contains one or more invalid UIDs, the kuid_t
* variables pointed to by 'parent' and 'child' will get updated but this
* variables pointed to by @parent and @child will get updated but this
* function will return an error.
* Contents of @buf may be modified.
*/
static int parse_safesetid_whitelist_policy(const char __user *buf,
size_t len,
kuid_t *parent,
kuid_t *child)
static int parse_policy_line(
struct file *file, char *buf, kuid_t *parent, kuid_t *child)
{
char *kern_buf;
char *parent_buf;
char *child_buf;
const char separator[] = ":";
char *child_str;
int ret;
size_t first_substring_length;
long parsed_parent;
long parsed_child;
u32 parsed_parent, parsed_child;
/* Duplicate string from user memory and NULL-terminate */
kern_buf = memdup_user_nul(buf, len);
if (IS_ERR(kern_buf))
return PTR_ERR(kern_buf);
/* Format of |buf| string should be <UID>:<UID>. */
child_str = strchr(buf, ':');
if (child_str == NULL)
return -EINVAL;
*child_str = '\0';
child_str++;
/*
* Format of |buf| string should be <UID>:<UID>.
* Find location of ":" in kern_buf (copied from |buf|).
*/
first_substring_length = strcspn(kern_buf, separator);
if (first_substring_length == 0 || first_substring_length == len) {
ret = -EINVAL;
goto free_kern;
}
parent_buf = kmemdup_nul(kern_buf, first_substring_length, GFP_KERNEL);
if (!parent_buf) {
ret = -ENOMEM;
goto free_kern;
}
ret = kstrtol(parent_buf, 0, &parsed_parent);
ret = kstrtou32(buf, 0, &parsed_parent);
if (ret)
goto free_both;
return ret;
child_buf = kern_buf + first_substring_length + 1;
ret = kstrtol(child_buf, 0, &parsed_child);
ret = kstrtou32(child_str, 0, &parsed_child);
if (ret)
goto free_both;
return ret;
*parent = make_kuid(current_user_ns(), parsed_parent);
if (!uid_valid(*parent)) {
ret = -EINVAL;
goto free_both;
}
*child = make_kuid(current_user_ns(), parsed_child);
if (!uid_valid(*child)) {
ret = -EINVAL;
goto free_both;
}
if (!uid_valid(*parent) || !uid_valid(*child))
return -EINVAL;
free_both:
kfree(parent_buf);
free_kern:
return 0;
}
static int parse_safesetid_whitelist_policy(
struct file *file, const char __user *buf, size_t len,
kuid_t *parent, kuid_t *child)
{
char *kern_buf = memdup_user_nul(buf, len);
int ret;
if (IS_ERR(kern_buf))
return PTR_ERR(kern_buf);
ret = parse_policy_line(file, kern_buf, parent, child);
kfree(kern_buf);
return ret;
}
@ -121,8 +103,8 @@ static ssize_t safesetid_file_write(struct file *file,
flush_safesetid_whitelist_entries();
break;
case SAFESETID_WHITELIST_ADD:
ret = parse_safesetid_whitelist_policy(buf, len, &parent,
&child);
ret = parse_safesetid_whitelist_policy(file, buf, len,
&parent, &child);
if (ret)
return ret;