Re: [Qemu-devel] [PATCH] pc_init: Fail on bad kernel

[Anthony Liguori <aliguori@us.ibm.com>]

On 09/03/2011 02:35 PM, Sasha Levin wrote:
> When providing QEMU with a bad '-kernel' parameter, such as a file which
> is not really a kernel, QEMU will attempt to allocate a huge amount of
> memory and fail either with "Failed to allocate memory: Cannot allocate
> memory" or a GLib error: "GLib-ERROR **: gmem.c:170: failed to allocate
> 18446744073709529965 bytes"
>
> This patch handles the case where the magic sig wasn't located in the
> provided kernel, and loading it as multiboot failed as well.
>
> Cc: Anthony Liguori<aliguori@us.ibm.com>
> Signed-off-by: Sasha Levin<levinsasha928@gmail.com>
> ---
>   hw/pc.c |    8 +++++++-
>   1 files changed, 7 insertions(+), 1 deletions(-)
>
> diff --git a/hw/pc.c b/hw/pc.c
> index 6b3662e..428440b 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -691,8 +691,14 @@ static void load_linux(void *fw_cfg,
>   	/* This looks like a multiboot kernel. If it is, let's stop
>   	   treating it like a Linux kernel. */
>           if (load_multiboot(fw_cfg, f, kernel_filename, initrd_filename,
> -                           kernel_cmdline, kernel_size, header))
> +                           kernel_cmdline, kernel_size, header)) {
>               return;
> +        } else {
> +            fprintf(stderr, "qemu: could not load kernel '%s': %s\n",
> +		    kernel_filename, strerror(errno));
> +	    exit(1);
> +        }
> +	

There's trailing whitespace on this line.

But I also don't think this is the right fix.  This change makes the 
line below unreachable.  There is still code in this path attempting to 
handle protocols < 2.00.  Admittedly, these would be ancient kernels 
that I doubt anyone would really use but the code is there to support it 
nonetheless.

I think a better fix would be to positively identify kernels that are 
older than this.

Perhaps hpa knows how we could positively identify a kernel that's older 
than protocol 200?

Regards,

Anthony Liguori

>   	protocol = 0;
>       }
>