ima: Generalize ima_write_policy() and raise uploaded data size limit

hulk inclusion
category: feature
feature: IMA Digest Lists extension
bugzilla: 46797

-------------------------------------------------

ima_write_policy() is being used to load a new policy from user space. This
function can be reused to load different types of data.

This patch renames ima_write_policy() to ima_write_data() and executes the
appropriate actions depending on the opened file in securityfs.

Also, this patch raises the uploaded data size limit to 64M, to accept
files (e.g. digest lists) larger than a policy. The same limit is used for
the SELinux policy.
Signed-off-by: NRoberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: NTianxing Zhang <zhangtianxing3@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

security/integrity/ima/ima_fs.c

@@ -336,26 +336,32 @@ static ssize_t ima_read_file(char *path, struct dentry *dentry)
 		return pathlen;
 }
 
-static ssize_t ima_write_policy(struct file *file, const char __user *buf,
+static ssize_t ima_write_data(struct file *file, const char __user *buf,
 			      size_t datalen, loff_t *ppos)
 {
 	char *data;
 	ssize_t result;
 	struct dentry *dentry = file_dentry(file);
 
-	if (datalen >= PAGE_SIZE)
-		datalen = PAGE_SIZE - 1;
-
 	/* No partial writes. */
 	result = -EINVAL;
 	if (*ppos != 0)
 		goto out;
 
-	data = memdup_user_nul(buf, datalen);
-	if (IS_ERR(data)) {
-		result = PTR_ERR(data);
+	result = -EFBIG;
+	if (datalen > 64 * 1024 * 1024 - 1)
 		goto out;
-	}
+
+	result = -ENOMEM;
+	data = vmalloc(datalen + 1);
+	if (!data)
+		goto out;
+
+	result = -EFAULT;
+	if (copy_from_user(data, buf, datalen) != 0)
+		goto out_free;
+
+	data[datalen] = '\0';
 
 	result = mutex_lock_interruptible(&ima_write_mutex);
 	if (result < 0)
@@ -363,20 +369,26 @@ static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 
 	if (data[0] == '/') {
 		result = ima_read_file(data, dentry);
-	} else if (ima_appraise & IMA_APPRAISE_POLICY) {
-		pr_err("signed policy file (specified as an absolute pathname) required\n");
+	} else if (dentry == ima_policy) {
+		if (ima_appraise & IMA_APPRAISE_POLICY) {
+			pr_err("signed policy file (specified "
+			       "as an absolute pathname) required\n");
 			integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
-				    "policy_update", "signed policy required",
-				    1, 0);
+					    "policy_update",
+					    "signed policy required", 1, 0);
 			result = -EACCES;
 		} else {
 			result = ima_parse_add_rule(data);
 		}
+	} else {
+		pr_err("Unknown data type\n");
+		result = -EINVAL;
+	}
 	mutex_unlock(&ima_write_mutex);
 out_free:
-	kfree(data);
+	vfree(data);
 out:
-	if (result < 0)
+	if (dentry == ima_policy && result < 0)
 		valid_policy = 0;
 
 	return result;
@@ -462,7 +474,7 @@ static int ima_release_policy(struct inode *inode, struct file *file)
 
 static const struct file_operations ima_measure_policy_ops = {
 	.open = ima_open_policy,
-	.write = ima_write_policy,
+	.write = ima_write_data,
 	.read = seq_read,
 	.release = ima_release_policy,
 	.llseek = generic_file_llseek,