On Fri, 14 Mar 2025 at 13:08, Ard Biesheuvel <ardb+git@xxxxxxxxxx> wrote: > > From: Ard Biesheuvel <ardb@xxxxxxxxxx> > > Ben reports spurious EFI zboot failures on a system where physical RAM > starts at 0x0. When doing random memory allocation from the EFI stub on > such a platform, a random seed of 0x0 (which means no entropy source is > available) will result in the allocation to be placed at address 0x0 if > sufficient space is available. > > When this allocation is subsequently passed on to the decompression > code, the 0x0 address is mistaken for NULL and the code complains and > gives up. > > So avoid address 0x0 when doing random allocation, and set the minimum > address to the minimum alignment. > > Reported-by: Ben Schneider <ben@xxxxxxxxx> > Tested-by: Ben Schneider <ben@xxxxxxxxx> > Cc: Ilias Apalodimas <ilias.apalodimas@xxxxxxxxxx> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > --- > drivers/firmware/efi/libstub/randomalloc.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c > index 5a732018be36..fd80b2f3233a 100644 > --- a/drivers/firmware/efi/libstub/randomalloc.c > +++ b/drivers/firmware/efi/libstub/randomalloc.c > @@ -75,6 +75,10 @@ efi_status_t efi_random_alloc(unsigned long size, > if (align < EFI_ALLOC_ALIGN) > align = EFI_ALLOC_ALIGN; > > + /* Avoid address 0x0, as it can be mistaken for NULL */ > + if (alloc_min == 0) > + alloc_min = align; > + > size = round_up(size, EFI_ALLOC_ALIGN); > > /* count the suitable slots in each memory map entry */ > -- > 2.49.0.rc1.451.g8f38331e32-goog > Reviewed-by: Ilias Apalodimas <ilias.apalodimas@xxxxxxxxxx>
