linux-kernel - Re: [PATCH] arm64: kdump: update ppos when reading elfcorehdr

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Date:   Fri, 19 Mar 2021 16:07:00 -0500
From:   Tyler Hicks <tyhicks@...ux.microsoft.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     jmorris@...ei.org, catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: kdump: update ppos when reading elfcorehdr

On 2021-03-19 16:50:54, Pavel Tatashin wrote:
> The ppos points to a position in the old kernel memory (and in case of
> arm64 in the crash kernel since elfcorehdr is passed as a segment). The
> function should update the ppos by the amount that was read. This bug is
> not exposed by accident, but other platforms update this value properly.
> So, fix it in ARM64 version of elfcorehdr_read() as well.
> 

Fixes: e62aaeac426a ("arm64: kdump: provide /proc/vmcore file")
Reviewed-by: Tyler Hicks <tyhicks@...ux.microsoft.com>

Tyler

> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> ---
>  arch/arm64/kernel/crash_dump.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kernel/crash_dump.c b/arch/arm64/kernel/crash_dump.c
> index e6e284265f19..58303a9ec32c 100644
> --- a/arch/arm64/kernel/crash_dump.c
> +++ b/arch/arm64/kernel/crash_dump.c
> @@ -64,5 +64,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
>  ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
>  {
>  	memcpy(buf, phys_to_virt((phys_addr_t)*ppos), count);
> +	*ppos += count;
> +
>  	return count;
>  }
> -- 
> 2.25.1
>