On Tue, Sep 16, 2008 at 03:18:23PM -0400, Jonathan Steel wrote:
> A segmentation fault can occur in kimage_add_entry in kexec.c when
> loading a kernel image into memory. The fault occurs because a page is
> requested by calling kimage_alloc_page with gfp_mask GFP_KERNEL and the
> function may actually return a page with gfp_mask GFP_HIGHUSER. The high
> mem page is returned because it was swapped with the kernel page due to
> the kernel page being a page that will shortly be copied to.
>
> This patch ensures that kimage_alloc_page returns a page that was
> created with the correct gfp flags.
I wonder if this problem might also affect other users of
kimage_alloc_pages(), and if so, perhaps it should guard
against this?
>
> --- linux-2.6.26.5.orig/kernel/kexec.c 2008-09-16 13:17:56.000000000
> -0400
> +++ linux-2.6.26.5/kernel/kexec.c 2008-09-16 13:26:35.000000000 -0400
> @@ -743,8 +743,15 @@ static struct page *kimage_alloc_page(st
> *old = addr | (*old & ~PAGE_MASK);
>
> /* The old page I have found cannot be a
> - * destination page, so return it.
> - */
> + * destination page, so return it if its
> + * gfp_flags honor the ones passed in.
> + */
> + if (!(gfp_mask & __GFP_HIGHMEM) &&
> + PageHighMem(old_page)) {
> + kimage_free_pages(old_page);
> + continue;
> + }
> +
> addr = old_addr;
> page = old_page;
> break;
>
> Signed-off-by: Jonathan Steel <jon.steel at esentire.com>
>
> Jonathan Steel
--
Simon Horman
VA Linux Systems Japan K.K., Sydney, Australia Satellite Office
H: www.vergenet.net/~horms/ W: www.valinux.co.jp/en
