kexec: replace call to copy_file_from_fd() with kernel version

Replace copy_file_from_fd() with kernel_read_file_from_fd().

Two new identifiers named READING_KEXEC_IMAGE and READING_KEXEC_INITRAMFS
are defined for measuring, appraising or auditing the kexec image and
initramfs.

Changelog v3:
- return -EBADF, not -ENOEXEC
- identifier change
- split patch, moving copy_file_from_fd() to a separate patch
- split patch, moving IMA changes to a separate patch
v0:
- use kstat file size type loff_t, not size_t
- Calculate the file hash from the in memory buffer - Dave Young

Signed-off-by: Mimi Zohar <[e-mail]>
Acked-by: Kees Cook <[e-mail]>
Acked-by: Luis R. Rodriguez <[e-mail]>
Cc: Eric Biederman <[e-mail]>
Acked-by: Dave Young <[e-mail]>

include/linux/fs.h

···
 enum kernel_read_file_id {
 	READING_FIRMWARE = 1,
 	READING_MODULE,
+	READING_KEXEC_IMAGE,
+	READING_KEXEC_INITRAMFS,
 	READING_MAX_ID
 };
 

kernel/kexec_file.c

···
 #include <linux/kexec.h>
 #include <linux/mutex.h>
 #include <linux/list.h>
+#include <linux/fs.h>
 #include <crypto/hash.h>
 #include <crypto/sha.h>
 #include <linux/syscalls.h>
···
 size_t __weak kexec_purgatory_size = 0;
 
 static int kexec_calculate_store_digests(struct kimage *image);
-
-static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len)
-{
-	struct fd f = fdget(fd);
-	int ret;
-	struct kstat stat;
-	loff_t pos;
-	ssize_t bytes = 0;
-
-	if (!f.file)
-		return -EBADF;
-
-	ret = vfs_getattr(&f.file->f_path, &stat);
-	if (ret)
-		goto out;
-
-	if (stat.size > INT_MAX) {
-		ret = -EFBIG;
-		goto out;
-	}
-
-	/* Don't hand 0 to vmalloc, it whines. */
-	if (stat.size == 0) {
-		ret = -EINVAL;
-		goto out;
-	}
-
-	*buf = vmalloc(stat.size);
-	if (!*buf) {
-		ret = -ENOMEM;
-		goto out;
-	}
-
-	pos = 0;
-	while (pos < stat.size) {
-		bytes = kernel_read(f.file, pos, (char *)(*buf) + pos,
-				    stat.size - pos);
-		if (bytes < 0) {
-			vfree(*buf);
-			ret = bytes;
-			goto out;
-		}
-
-		if (bytes == 0)
-			break;
-		pos += bytes;
-	}
-
-	if (pos != stat.size) {
-		ret = -EBADF;
-		vfree(*buf);
-		goto out;
-	}
-
-	*buf_len = pos;
-out:
-	fdput(f);
-	return ret;
-}
 
 /* Architectures can provide this probe function */
 int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
···
 {
 	int ret = 0;
 	void *ldata;
+	loff_t size;
 
-	ret = copy_file_from_fd(kernel_fd, &image->kernel_buf,
-				&image->kernel_buf_len);
+	ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
+				       &size, INT_MAX, READING_KEXEC_IMAGE);
 	if (ret)
 		return ret;
+	image->kernel_buf_len = size;
 
 	/* Call arch image probe handlers */
 	ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
 					    image->kernel_buf_len);
-
 	if (ret)
 		goto out;
 
···
 #endif
 	/* It is possible that there no initramfs is being loaded */
 	if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
-		ret = copy_file_from_fd(initrd_fd, &image->initrd_buf,
-					&image->initrd_buf_len);
+		ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
+					       &size, INT_MAX,
+					       READING_KEXEC_INITRAMFS);
 		if (ret)
 			goto out;
+		image->initrd_buf_len = size;
 	}
 
 	if (cmdline_len) {