From: Yinghai Lu Date: Fri, 20 Feb 2015 04:18:03 +0000 (-0800) Subject: efi/libstub: Fix boundary checking in efi_high_alloc() X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=7ed620bb343f434f8a85f830020c04988df2a140;p=deliverable%2Flinux.git efi/libstub: Fix boundary checking in efi_high_alloc() While adding support loading kernel and initrd above 4G to grub2 in legacy mode, I was referring to efi_high_alloc(). That will allocate buffer for kernel and then initrd, and initrd will use kernel buffer start as limit. During testing found two buffers will be overlapped when initrd size is very big like 400M. It turns out efi_high_alloc() boundary checking is not right. end - size will be the new start, and should not compare new start with max, we need to make sure end is smaller than max. [ Basically, with the current efi_high_alloc() code it's possible to allocate memory above 'max', because efi_high_alloc() doesn't check that the tail of the allocation is below 'max'. If you have an EFI memory map with a single entry that looks like so, [0xc0000000-0xc0004000] And want to allocate 0x3000 bytes below 0xc0003000 the current code will allocate [0xc0001000-0xc0004000], not [0xc0000000-0xc0003000] like you would expect. - Matt ] Signed-off-by: Yinghai Lu Reviewed-by: Ard Biesheuvel Reviewed-by: Mark Rutland Tested-by: Mark Rutland Cc: Signed-off-by: Matt Fleming --- diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c index 9bd9fbb5bea8..c927bccd92bd 100644 --- a/drivers/firmware/efi/libstub/efi-stub-helper.c +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c @@ -170,12 +170,12 @@ again: start = desc->phys_addr; end = start + desc->num_pages * (1UL << EFI_PAGE_SHIFT); - if ((start + size) > end || (start + size) > max) - continue; - - if (end - size > max) + if (end > max) end = max; + if ((start + size) > end) + continue; + if (round_down(end - size, align) < start) continue;