Re: [PATCH] arm/efi: Fix null pointer dereference

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 11 Oct 2021, Bertrand Marquis wrote:
> Hi Luca,
> 
> > On 11 Oct 2021, at 08:56, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
> > 
> > Fix for commit 60649d443dc395243e74d2b3e05594ac0c43cfe3
> > that introduces a null pointer dereference when the
> > fdt_node_offset_by_compatible is called with "fdt"
> > argument null.
> > 
> > Reported-by: Julien Grall <julien@xxxxxxx>
> > Fixes: 60649d443d ("arm/efi: Introduce xen,uefi-cfg-load DT property")
> > Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
> Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> > ---
> > xen/arch/arm/efi/efi-boot.h | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> > index a3e46453d4..e63dafac26 100644
> > --- a/xen/arch/arm/efi/efi-boot.h
> > +++ b/xen/arch/arm/efi/efi-boot.h
> > @@ -593,7 +593,8 @@ static bool __init 
> > efi_arch_use_config_file(EFI_SYSTEM_TABLE *SystemTable)
> >     dtbfile.ptr = fdt;
> >     dtbfile.need_to_free = false; /* Config table memory can't be freed. */
> > 
> > -    if ( fdt_node_offset_by_compatible(fdt, 0, "multiboot,module") > 0 )
> > +    if ( fdt &&
> > +         (fdt_node_offset_by_compatible(fdt, 0, "multiboot,module") > 0) )
> >     {
> >         /* Locate chosen node */
> >         int node = fdt_subnode_offset(fdt, 0, "chosen");
> > -- 
> > 2.17.1
> > 
>