This commit introduces integer underflow mitigation in max_addr calculation
in grub_relocator_alloc_chunk_align() invocation.
It consists of 2 fixes:
1. Introduced grub_relocator_alloc_chunk_align_safe() wrapper function to perform
sanity check for min/max and size values, and to make safe invocation of
grub_relocator_alloc_chunk_align() with validated max_addr value. Replace all
invocations such as grub_relocator_alloc_chunk_align(..., min_addr, max_addr - size, size, ...)
by grub_relocator_alloc_chunk_align_safe(..., min_addr, max_addr, size, ...).
2. Introduced UP_TO_TOP32(s) macro for the cases where max_addr is 32-bit top
address (0xffffffff - size + 1) or similar.
Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This modifies most of the places we do some form of:
X = malloc(Y * Z);
to use calloc(Y, Z) instead.
Among other issues, this fixes:
- allocation of integer overflow in grub_png_decode_image_header()
reported by Chris Coulson,
- allocation of integer overflow in luks_recover_key()
reported by Chris Coulson,
- allocation of integer overflow in grub_lvm_detect()
reported by Chris Coulson.
Fixes: CVE-2020-14308
Signed-off-by: Peter Jones <pjones@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Without that fix we have:
In file included from ../../include/grub/command.h:25:0,
from ../../grub-core/loader/multiboot.c:30:
../../grub-core/loader/multiboot_elfxx.c: In function 'grub_multiboot_load_elf64':
../../grub-core/loader/multiboot_elfxx.c:130:28: error: 'relocatable' undeclared (first use in this function)
"load_base_addr=0x%x\n", relocatable,
This happens due to mistake in the commit 14ec665
(mbi: Use per segment a separate relocator chunk).
So, let's fix it.
Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Instead of setting up a all comprising relocator chunk for all segments,
use per segment a separate relocator chunk.
Currently, if the ELF is non-relocatable, a single relocator chunk will
comprise memory (between the segments) which gets overridden by the relst()
invocation of the movers code in grub_relocator16/32/64_boot().
The overridden memory may contain reserved ranges like VGA memory or ACPI
tables, which may lead to crashes or at least to strange boot behaviour.
Signed-off-by: Alexander Boettcher <alexander.boettcher@genode-labs.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Previously we had multiboot and multiboot2 declaring the same symbols.
This can potentially lead to aliasing and strange behaviours when e.g.
module instead of module2 is used with multiboot2.
Bug: #51137
Currently multiboot2 protocol loads image exactly at address specified in
ELF or multiboot2 header. This solution works quite well on legacy BIOS
platforms. It is possible because memory regions are placed at predictable
addresses (though I was not able to find any spec which says that it is
strong requirement, so, it looks that it is just a goodwill of hardware
designers). However, EFI platforms are more volatile. Even if required
memory regions live at specific addresses then they are sometimes simply
not free (e.g. used by boot/runtime services on Dell PowerEdge R820 and
OVMF). This means that you are not able to just set up final image
destination on build time. You have to provide method to relocate image
contents to real load address which is usually different than load address
specified in ELF and multiboot2 headers.
This patch provides all needed machinery to do self relocation in image code.
First of all GRUB2 reads min_addr (min. load addr), max_addr (max. load addr),
align (required image alignment), preference (it says which memory regions are
preferred by image, e.g. none, low, high) from multiboot_header_tag_relocatable
header tag contained in binary (at this stage load addresses from multiboot2
and/or ELF headers are ignored). Later loader tries to fulfill request (not only
that one) and if it succeeds then it informs image about real load address via
multiboot_tag_load_base_addr tag. At this stage GRUB2 role is finished. Starting
from now executable must cope with relocations itself using whole static and
dynamic knowledge provided by boot loader.
This patch does not provide functionality which could do relocations using
ELF relocation data. However, I was asked by Konrad Rzeszutek Wilk and Vladimir
'phcoder' Serbinenko to investigate that thing. It looks that relevant machinery
could be added to existing code (including this patch) without huge effort.
Additionally, ELF relocation could live in parallel with self relocation provided
by this patch. However, during research I realized that first of all we should
establish the details how ELF relocatable image should look like and how it should
be build. At least to build proper test/example files.
So, this patch just provides support for self relocatable images. If ELF file
with relocs is loaded then GRUB2 complains loudly and ignores it. Support for
such files will be added later.
This patch was tested with Xen image which uses that functionality. However, this Xen
feature is still under development and new patchset will be released in about 2-3 weeks.
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
