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authorArd Biesheuvel <ardb@kernel.org>2022-08-04 16:39:48 +0300
committerArd Biesheuvel <ardb@kernel.org>2022-09-22 11:12:51 +0300
commit63bf28ceb3ebbe76048c3fb2987996ca1ae64f83 (patch)
tree260b37eb1d7834dc22d29176d1c5c822412009c4 /drivers/firmware
parent7da5b13dccd99cfdc42940fc7adcb88647023292 (diff)
downloadlinux-63bf28ceb3ebbe76048c3fb2987996ca1ae64f83.tar.xz
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>
Diffstat (limited to 'drivers/firmware')
-rw-r--r--drivers/firmware/efi/libstub/x86-stub.c7
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 43ca665af610..7a7abc8959d2 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 */