[PATCH v4 09/19] vfs: define kernel_read_file_from_path

[Mimi Zohar]

This patch defines kernel_read_file_from_path(), a wrapper for the VFS
common kernel_read_file().

Changelog:
- Separated from the IMA patch

Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
Acked-by: Kees Cook <keescook at chromium.org>
Acked-by: Luis R. Rodriguez <mcgrof at kernel.org>
Cc: Al Viro <viro at zeniv.linux.org.uk>
---
 fs/exec.c          | 22 ++++++++++++++++++++++
 include/linux/fs.h |  2 ++
 2 files changed, 24 insertions(+)

diff --git a/fs/exec.c b/fs/exec.c
index 1138dc5..67816a0 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -884,6 +884,28 @@ out:
 }
 EXPORT_SYMBOL_GPL(kernel_read_file);
 
+int kernel_read_file_from_path(char *path, void **buf, loff_t *size,
+			       loff_t max_size, enum kernel_read_file_id id)
+{
+	struct file *file;
+	int ret;
+
+	if (!path || !*path)
+		return -EINVAL;
+
+	file = filp_open(path, O_RDONLY, 0);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		pr_err("Unable to open file: %s (%d)", path, ret);
+		return ret;
+	}
+
+	ret = kernel_read_file(file, buf, size, max_size, id);
+	fput(file);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
+
 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 {
 	ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index aa84bcb..00fa5c4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2583,6 +2583,8 @@ enum kernel_read_file_id {
 extern int kernel_read(struct file *, loff_t, char *, unsigned long);
 extern int kernel_read_file(struct file *, void **, loff_t *, loff_t,
 			    enum kernel_read_file_id);
+extern int kernel_read_file_from_path(char *, void **, loff_t *, loff_t,
+				      enum kernel_read_file_id);
 extern ssize_t kernel_write(struct file *, const char *, size_t, loff_t);
 extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
 extern struct file * open_exec(const char *);
-- 
2.1.0