Received-SPF: pass (google.com: domain of linux-kernel+bounces-1518-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
From: "Eric W. Biederman" <ebiederm@xmission.com>
To: Yuntao Wang <ytcoode@gmail.com>
Cc: linux-kernel@vger.kernel.org,  kexec@lists.infradead.org,
  x86@kernel.org,  Andrew Morton <akpm@linux-foundation.org>,  Thomas
 Gleixner <tglx@linutronix.de>,  Ingo Molnar <mingo@redhat.com>,  Borislav
 Petkov <bp@alien8.de>,  Dave Hansen <dave.hansen@linux.intel.com>,  "H.
 Peter Anvin" <hpa@zytor.com>,  Jonathan Corbet <corbet@lwn.net>
References: <20231215080910.173338-1-ytcoode@gmail.com>
	<20231215080910.173338-2-ytcoode@gmail.com>
Date: Fri, 15 Dec 2023 11:46:28 -0600
In-Reply-To: <20231215080910.173338-2-ytcoode@gmail.com> (Yuntao Wang's
	message of "Fri, 15 Dec 2023 16:09:08 +0800")
Message-ID: <87a5qb4avf.fsf@email.froward.int.ebiederm.org>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux)
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [PATCH 1/3] kexec_file: fix incorrect end value passed to
 kimage_is_destination_range()

Yuntao Wang <ytcoode@gmail.com> writes:

> 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. Fix
> it.

If that is true we I think we should rather fix
kimage_is_destination_range.

Otherwise we run the risk of having areas whose end is not
representable, epecially on 32bit.


Eric


> Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
> ---
>  kernel/kexec_file.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index f9a419cd22d4..26be070d3bdd 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -435,13 +435,12 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
>  		if (temp_start < start || temp_start < kbuf->buf_min)
>  			return 0;
>  
> -		temp_end = temp_start + kbuf->memsz - 1;
> -
>  		/*
>  		 * Make sure this does not conflict with any of existing
>  		 * segments
>  		 */
> -		if (kimage_is_destination_range(image, temp_start, temp_end)) {
> +		if (kimage_is_destination_range(image, temp_start,
> +						temp_start + kbuf->memsz)) {
>  			temp_start = temp_start - PAGE_SIZE;
>  			continue;
>  		}
> @@ -475,7 +474,7 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
>  		 * Make sure this does not conflict with any of existing
>  		 * segments
>  		 */
> -		if (kimage_is_destination_range(image, temp_start, temp_end)) {
> +		if (kimage_is_destination_range(image, temp_start, temp_end + 1)) {
>  			temp_start = temp_start + PAGE_SIZE;
>  			continue;
>  		}