The UEFI stub executes in the context of the firmware, which identity maps the available system RAM, which implies that only memory below 4 GB can be used for allocations on 32-bit architectures, even on [L]PAE capable hardware. So ignore any reported memory above 4 GB in efi_random_alloc(). This also fixes a reported build problem on ARM under -Os, where the 64-bit logical shift relies on a software routine that the ARM decompressor does not provide. A second [minor] issue is also fixed, where the '+ 1' is moved out of the shift, where it belongs: the reason for its presence is that a memory region where start == end should count as a single slot, given that end takes the the desired size and alignment of the allocation into account. Reported-by: Arnd Bergmann <arnd@xxxxxxxx> Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> --- drivers/firmware/efi/libstub/random.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c index 3a3feacc329f..c95f1f65d0ed 100644 --- a/drivers/firmware/efi/libstub/random.c +++ b/drivers/firmware/efi/libstub/random.c @@ -54,10 +54,13 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md, end = round_down(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - size, align); + if (end > ULONG_MAX) + end = ULONG_MAX + 1; + if (start > end) return 0; - return (end - start + 1) >> align_shift; + return ((unsigned long)(end - start) >> align_shift) + 1; } /* -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
