Re: [Qemu-devel] [qemu-s390x] [PATCH v2] hw/s390x/ipl: Fix crashes that occurs when -kernel is used with small images

[Thomas Huth <thuth@redhat.com>]

On 11.06.2018 19:26, Thomas Huth wrote:
> Add a sanity checks to fix the following two crashes:
> 
> $ echo "Insane in the mainframe" > /tmp/test.txt
> $ s390x-softmmu/qemu-system-s390x -kernel /tmp/test.txt -append xyz
> Segmentation fault (core dumped)
> $ s390x-softmmu/qemu-system-s390x -kernel /tmp/test.txt -initrd /tmp/test.txt
> Segmentation fault (core dumped)
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  v2: Fixed 2nd crash with -initrd
> 
>  hw/s390x/ipl.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
> index 04245b5..2ff8f20 100644
> --- a/hw/s390x/ipl.c
> +++ b/hw/s390x/ipl.c
> @@ -168,7 +168,8 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
>           * we can not rely on the ELF entry point - it was 0x800 (the SALIPL
>           * loader) and it won't work. For this case we force it to 0x10000, too.
>           */
> -        if (pentry == KERN_IMAGE_START || pentry == 0x800) {
> +        if ((pentry == KERN_IMAGE_START || pentry == 0x800) &&
> +            kernel_size > KERN_PARM_AREA + strlen(ipl->cmdline)) {
>              ipl->start_addr = KERN_IMAGE_START;
>              /* Overwrite parameters in the kernel image, which are "rom" */
>              strcpy(rom_ptr(KERN_PARM_AREA), ipl->cmdline);
> @@ -195,8 +196,10 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
>               * we have to overwrite values in the kernel image,
>               * which are "rom"
>               */
> -            stq_p(rom_ptr(INITRD_PARM_START), initrd_offset);
> -            stq_p(rom_ptr(INITRD_PARM_SIZE), initrd_size);
> +            if (kernel_size > INITRD_PARM_SIZE + 8) {
> +                stq_p(rom_ptr(INITRD_PARM_START), initrd_offset);
> +                stq_p(rom_ptr(INITRD_PARM_SIZE), initrd_size);
> +            }
>          }
>      }
>      /*

I just had to discover that this breaks the argv handling in
kvm-unit-tests. Cornelia, could you please unqueue this patch again?
I'll try to come up with a better solution...

 Thomas