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| author | Ard Biesheuvel <ardb@kernel.org> | 2022-08-04 15:39:48 +0200 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2022-09-22 10:12:51 +0200 |
| commit | 63bf28ceb3ebbe76048c3fb2987996ca1ae64f83 (patch) | |
| tree | 260b37eb1d7834dc22d29176d1c5c822412009c4 | |
| parent | 7da5b13dccd99cfdc42940fc7adcb88647023292 (diff) | |
| download | linux-63bf28ceb3ebbe76048c3fb2987996ca1ae64f83.tar.gz | |
efi: x86: Wipe setup_data on pure EFI boot
When booting the x86 kernel via EFI using the LoadImage/StartImage boot
services [as opposed to the deprecated EFI handover protocol], the setup
header is taken from the image directly, and given that EFI's LoadImage
has no Linux/x86 specific knowledge regarding struct bootparams or
struct setup_header, any absolute addresses in the setup header must
originate from the file and not from a prior loading stage.
Since we cannot generally predict where LoadImage() decides to load an
image (*), such absolute addresses must be treated as suspect: even if a
prior boot stage intended to make them point somewhere inside the
[signed] image, there is no way to validate that, and if they point at
an arbitrary location in memory, the setup_data nodes will not be
covered by any signatures or TPM measurements either, and could be made
to contain an arbitrary sequence of SETUP_xxx nodes, which could
interfere quite badly with the early x86 boot sequence.
(*) Note that, while LoadImage() does take a buffer/size tuple in
addition to a device path, which can be used to provide the image
contents directly, it will re-allocate such images, as the memory
footprint of an image is generally larger than the PE/COFF file
representation.
Cc: <stable@vger.kernel.org> # v5.10+
Link: https://lore.kernel.org/all/20220904165321.1140894-1-Jason@zx2c4.com/
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
| -rw-r--r-- | drivers/firmware/efi/libstub/x86-stub.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index 43ca665af610c4..7a7abc8959d2b0 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -516,6 +516,13 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle, hdr->ramdisk_image = 0; hdr->ramdisk_size = 0; + /* + * Disregard any setup data that was provided by the bootloader: + * setup_data could be pointing anywhere, and we have no way of + * authenticating or validating the payload. + */ + hdr->setup_data = 0; + efi_stub_entry(handle, sys_table_arg, boot_params); /* not reached */ |