linux-kernel - Re: [PATCH 1/3 v4] kexec: modify the meaning of the end parameter in kimage_is_destination

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Date: Sun, 17 Dec 2023 09:02:03 +0800
From: Baoquan He <bhe@...hat.com>
To: Yuntao Wang <ytcoode@...il.com>
Cc: akpm@...ux-foundation.org, bp@...en8.de, corbet@....net,
	dave.hansen@...ux.intel.com, ebiederm@...ssion.com, hpa@...or.com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	mingo@...hat.com, tglx@...utronix.de, x86@...nel.org
Subject: Re: [PATCH 1/3 v4] kexec: modify the meaning of the end parameter in
 kimage_is_destination_range()

On 12/16/23 at 08:05pm, Yuntao Wang wrote:
> The end parameter received by kimage_is_destination_range() should be the
> last valid byte address of the target memory segment plus 1. However, in
> the locate_mem_hole_bottom_up() and locate_mem_hole_top_down() functions,
> the corresponding value passed to kimage_is_destination_range() is the last
> valid byte address of the target memory segment, which is 1 less.
> 
> There are two ways to fix this bug. We can either correct the logic of the
> locate_mem_hole_bottom_up() and locate_mem_hole_top_down() functions, or we
> can fix kimage_is_destination_range() by making the end parameter represent
> the last valid byte address of the target memory segment. Here, we choose
> the second approach.
> 
> Due to the modification to kimage_is_destination_range(), we also need to
> adjust its callers, such as kimage_alloc_normal_control_pages() and
> kimage_alloc_page().
> 
> Signed-off-by: Yuntao Wang <ytcoode@...il.com>
> ---
> v1->v2:
>   Fix this issue using the approach suggested by Eric and Baoquan.
> 
>   As this patch is independent of the other patches in this series, I sent
>   out the v2 patch separately. If it's inconvenient for anyone, I can
>   resend the entire series again.
> 
> v2->v3:
>   Modify the assignment of eaddr as suggested by Baoquan.
> 
> v3->v4:
>   `eaddr = epfn << PAGE_SHIFT - 1` causes a compilation warning, fix it.
> 
>  kernel/kexec_core.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

The whole series looks good to me with this v4 of patch 1, you may need
to reorganize them and repost.

Acked-by: Baoquan He <bhe@...hat.com>

> 
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index be5642a4ec49..e3b1a699f087 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -276,8 +276,8 @@ int kimage_is_destination_range(struct kimage *image,
>  		unsigned long mstart, mend;
>  
>  		mstart = image->segment[i].mem;
> -		mend = mstart + image->segment[i].memsz;
> -		if ((end > mstart) && (start < mend))
> +		mend = mstart + image->segment[i].memsz - 1;
> +		if ((end >= mstart) && (start <= mend))
>  			return 1;
>  	}
>  
> @@ -370,7 +370,7 @@ static struct page *kimage_alloc_normal_control_pages(struct kimage *image,
>  		pfn   = page_to_boot_pfn(pages);
>  		epfn  = pfn + count;
>  		addr  = pfn << PAGE_SHIFT;
> -		eaddr = epfn << PAGE_SHIFT;
> +		eaddr = (epfn << PAGE_SHIFT) - 1;
>  		if ((epfn >= (KEXEC_CONTROL_MEMORY_LIMIT >> PAGE_SHIFT)) ||
>  			      kimage_is_destination_range(image, addr, eaddr)) {
>  			list_add(&pages->lru, &extra_pages);
> @@ -716,7 +716,7 @@ static struct page *kimage_alloc_page(struct kimage *image,
>  
>  		/* If the page is not a destination page use it */
>  		if (!kimage_is_destination_range(image, addr,
> -						  addr + PAGE_SIZE))
> +						  addr + PAGE_SIZE - 1))
>  			break;
>  
>  		/*
> -- 
> 2.43.0
>