Re: [PATCH 03/13] kexec: Move segment verification code in a separate function

Borislav Petkov
2014-06-04T09:33:41Z

On Tue, Jun 03, 2014 at 09:06:52AM -0400, Vivek Goyal wrote:
> Previously do_kimage_alloc() will allocate a kimage structure, copy
> segment list from user space and then do the segment list sanity verification.
>
> Break down this function in 3 parts. do_kimage_alloc_init() to do actual
> allocation and basic initialization of kimage structure.
> copy_user_segment_list() to copy segment list from user space and
> sanity_check_segment_list() to verify the sanity of segment list as passed
> by user space.
>
> In later patches, I need to only allocate kimage and not copy segment
> list from user space. So breaking down in smaller functions enables
> re-use of code at other places.

I haven't seen what's going on further in the patchset but from looking at
kimage_normal_alloc() and kimage_crash_alloc()'s guts, they look very
similar and could probably share a common __kimage_alloc which does
do_kimage_alloc_init, copy_user_segment_list, sanity_check_segment_list
and kimage_alloc_control_pages...

One probably would have to actually write it down to see whether it
makes sense though and is not too ugly :-)

> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---

In any case, it looks ok, just two nitpicks below:

Acked-by: Borislav Petkov <bp@suse.de>

> kernel/kexec.c | 182 ++++++++++++++++++++++++++++++++-------------------------
> 1 file changed, 101 insertions(+), 81 deletions(-)

...

> +static struct kimage *do_kimage_alloc_init(void)
> +{
> + struct kimage *image;
> +
> + /* Allocate a controlling structure */
> + image = kzalloc(sizeof(*image), GFP_KERNEL);
> + if (!image)
> + return NULL;
> +
> + image->head = 0;
> + image->entry = &image->head;
> + image->last_entry = &image->head;
> + image->control_page = ~0; /* By default this does not apply */
> + image->type = KEXEC_TYPE_DEFAULT;
> +
> + /* Initialize the list of control pages */
> + INIT_LIST_HEAD(&image->control_pages);
> +
> + /* Initialize the list of destination pages */
> + INIT_LIST_HEAD(&image->dest_pages);
> +
> + /* Initialize the list of unusable pages */
> + INIT_LIST_HEAD(&image->unuseable_pages);

If the "e" in "unuseable" bugs you too, like me, you could add this one
to your patchset :-)

http://lkml.kernel.org/r/1392819695-24116-1-git-send-email-bp@alien8.de

...

> @@ -258,22 +292,23 @@ static int kimage_normal_alloc(struct kimage **rimage, unsigned long entry,
> get_order(KEXEC_CONTROL_PAGE_SIZE));
> if (!image->control_code_page) {
> printk(KERN_ERR "Could not allocate control_code_buffer\n");
> - goto out_free;
> + goto out_free_image;
> }
>
> image->swap_page = kimage_alloc_control_pages(image, 0);
> if (!image->swap_page) {
> printk(KERN_ERR "Could not allocate swap buffer\n");
> - goto out_free;
> + goto out_free_control_pages;
> }
>
> *rimage = image;
> return 0;
>
> -out_free:
> +

Superfluous newline.

> +out_free_control_pages:
> kimage_free_page_list(&image->control_pages);
> +out_free_image:
> kfree(image);
> -out:
> return result;
> }
>

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
--