On Thu, 23 May 2019 at 02:51, Gen Zhang <blackgod016574@xxxxxxxxx> wrote: > > In efi_call_phys_prolog(), save_pgd is allocated by kmalloc_array(). > And it is dereferenced in the following codes. However, memory > allocation functions such as kmalloc_array() may fail. Dereferencing > this save_pgd null pointer may cause the kernel go wrong. Thus we > should check this allocation. > Further, if efi_call_phys_prolog() returns NULL, we should abort the > process in phys_efi_set_virtual_address_map(), and return EFI_ABORTED. > > Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx> > > --- > diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c > index e1cb01a..a7189a3 100644 > --- a/arch/x86/platform/efi/efi.c > +++ b/arch/x86/platform/efi/efi.c > @@ -85,6 +85,8 @@ static efi_status_t __init phys_efi_set_virtual_address_map( > pgd_t *save_pgd; > > save_pgd = efi_call_phys_prolog(); > + if (!save_pgd) > + return EFI_ABORTED; > > /* Disable interrupts around EFI calls: */ > local_irq_save(flags); > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c > index cf0347f..828460a 100644 > --- a/arch/x86/platform/efi/efi_64.c > +++ b/arch/x86/platform/efi/efi_64.c > @@ -91,6 +91,8 @@ pgd_t * __init efi_call_phys_prolog(void) > > n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE); > save_pgd = kmalloc_array(n_pgds, sizeof(*save_pgd), GFP_KERNEL); > + if (!save_pgd) > + return NULL; > > /* > * Build 1:1 identity mapping for efi=old_map usage. Note that > --- Apologies for only spotting this now, but I seem to have given some bad advice. efi_call_phys_prolog() in efi_64.c will also return NULL if (!efi_enabled(EFI_OLD_MEMMAP)), but this is not an error condition. So that occurrence has to be updated: please return efi_mm.pgd instead.
