efi/x86: Avoid RWX mappings for all of DRAM

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The EFI code creates RWX mappings for all memory regions that are
occupied after the stub completes, and in the mixed mode case, it
even creates RWX mappings for all of the remaining DRAM as well.

Let's try to avoid this, by setting the NX bit for all memory
regions except the ones that are marked as EFI runtime services
code [which means text+rodata+data in practice, so we cannot mark
them read-only right away]. For cases of buggy firmware where boot
services code is called during SetVirtualAddressMap(), map those
regions with exec permissions as well - they will be unmapped in
efi_free_boot_services().

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200113172245.27925-7-ardb@kernel.org

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Ard Biesheuvel 2020-01-13 18:22:38 +01:00 • committed by Ingo Molnar

parent d9e3d2c4f1

commit 97bb9cdc32

1 changed files with 16 additions and 4 deletions

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arch/x86/platform/efi/efi_64.c

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