Re: [PATCH v3 18/22] kexec: replace call to copy_file_from_fd() with kernel version

[Dave Young <dyoung@redhat.com>]

On 02/03/16 at 02:06pm, Mimi Zohar wrote:
> 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
> - moved copy_file_from_fd() to a separate patch
> - defer support for IMA
> v1:
> - re-order and squash the kexec patches
> v0: ima: measure and appraise kexec image and initramfs (squashed)
> - rename ima_read_hooks enumeration to ima_policy_id
> - use kstat file size type loff_t, not size_t
> - add union name "hooks" to fix sparse warning
> - Calculate the file hash from the in memory buffer
> (suggested by Dave Young)
> - Rename ima_read_and_process_file() to ima_hash_and_process_file()
> - replace individual case statements with range:
>         KEXEC_CHECK ... IMA_MAX_READ_CHECK - 1
> - Instead of ima_read_and_process_file() allocating memory, the caller
> allocates and frees the memory.
> - Moved the kexec measurement/appraisal call to copy_file_from_fd(). The
> same call now measures and appraises both the kexec image and initramfs.
> 
> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> ---
>  include/linux/fs.h  |  2 ++
>  kernel/kexec_file.c | 73 +++++++----------------------------------------------
>  2 files changed, 11 insertions(+), 64 deletions(-)
> 
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9e1f1e3..d4d556e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2529,6 +2529,8 @@ extern int do_pipe_flags(int *, int);
>  enum kernel_read_file_id {
>  	READING_FIRMWARE = 1,
>  	READING_MODULE,
> +	READING_KEXEC_IMAGE,
> +	READING_KEXEC_INITRAMFS,
>  	READING_MAX_ID
>  };
>  
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index b70ada0..1443f93 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -18,6 +18,7 @@
>  #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>
> @@ -33,65 +34,6 @@ 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,
>  					 unsigned long buf_len)
> @@ -180,16 +122,17 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
>  {
>  	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;
>  
> @@ -204,10 +147,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
>  #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) {

Acked-by: Dave Young <dyoung@redhat.com>

Thanks
Dave