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kexec: fix segmentation fault in kimage_add_entry

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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 have verified the change and fixed the whitespace damage of the original
patch.  Jonathan did a great job of tracking this down after he hit the
problem.  -- Eric

Signed-off-by: Jonathan Steel <[email protected]>
Signed-off-by: Eric W. Biederman <[email protected]>
Acked-by: Simon Horman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Jonathan Steel 2008-09-22 13:57:45 -07:00 • committed by Linus Torvalds
commit f9092f358b
1 changed files with 7 additions and 1 deletions
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8
kernel/kexec.c
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@ -753,8 +753,14 @@ static struct page *kimage_alloc_page(struct kimage *image,
*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 it's
* 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;