linux-kernel - Re: [PATCH] initramfs: Don't free a non-existent initrd

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Message-Id: <20190516151145.GH19122@rapoport-lnx>
Date:   Thu, 16 May 2019 18:11:45 +0300
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Steven Price <steven.price@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] initramfs: Don't free a non-existent initrd

On Thu, May 16, 2019 at 03:31:25PM +0100, Steven Price wrote:
> Since 54c7a8916a88 ("initramfs: free initrd memory if opening
> /initrd.image fails"), the kernel has unconditionally attempted to free
> the initrd even if it doesn't exist. In the non-existent case this
> causes a boot-time splat if CONFIG_DEBUG_VIRTUAL is enabled due to a
> call to virt_to_phys() with a NULL address.
> 
> Instead we should check that the initrd actually exists and only attempt
> to free it if it does.
> 
> Fixes: 54c7a8916a88 ("initramfs: free initrd memory if opening /initrd.image fails")
> Reported-by: Mark Rutland <mark.rutland@....com>
> Tested-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---

Reviewed-by: Mike Rapoport <rppt@...ux.ibm.com>

>  init/initramfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/init/initramfs.c b/init/initramfs.c
> index 435a428c2af1..178130fd61c2 100644
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -669,7 +669,7 @@ static int __init populate_rootfs(void)
>  	 * If the initrd region is overlapped with crashkernel reserved region,
>  	 * free only memory that is not part of crashkernel region.
>  	 */
> -	if (!do_retain_initrd && !kexec_free_initrd())
> +	if (!do_retain_initrd && initrd_start && !kexec_free_initrd())
>  		free_initrd_mem(initrd_start, initrd_end);
>  	initrd_start = 0;
>  	initrd_end = 0;
> -- 
> 2.20.1
> 

-- 
Sincerely yours,
Mike.