From 5de0fef0230f3c8d75cff450a71740a7bf2db866 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Sat, 2 Feb 2019 10:41:12 +0100 Subject: efi/memattr: Don't bail on zero VA if it equals the region's PA The EFI memory attributes code cross-references the EFI memory map with the more granular EFI memory attributes table to ensure that they are in sync before applying the strict permissions to the regions it describes. Since we always install virtual mappings for the EFI runtime regions to which these strict permissions apply, we currently perform a sanity check on the EFI memory descriptor, and ensure that the EFI_MEMORY_RUNTIME bit is set, and that the virtual address has been assigned. However, in cases where a runtime region exists at physical address 0x0, and the virtual mapping equals the physical mapping, e.g., when running in mixed mode on x86, we encounter a memory descriptor with the runtime attribute and virtual address 0x0, and incorrectly draw the conclusion that a runtime region exists for which no virtual mapping was installed, and give up altogether. The consequence of this is that firmware mappings retain their read-write-execute permissions, making the system more vulnerable to attacks. So let's only bail if the virtual address of 0x0 has been assigned to a physical region that does not reside at address 0x0. Signed-off-by: Ard Biesheuvel Acked-by: Sai Praneeth Prakhya Cc: AKASHI Takahiro Cc: Alexander Graf Cc: Bjorn Andersson Cc: Borislav Petkov Cc: Heinrich Schuchardt Cc: Jeffrey Hugo Cc: Lee Jones Cc: Leif Lindholm Cc: Linus Torvalds Cc: Matt Fleming Cc: Peter Jones Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Fixes: 10f0d2f577053 ("efi: Implement generic support for the Memory ...") Link: http://lkml.kernel.org/r/20190202094119.13230-4-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar --- drivers/firmware/efi/memattr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/firmware') diff --git a/drivers/firmware/efi/memattr.c b/drivers/firmware/efi/memattr.c index 8986757eafaf..aac972b056d9 100644 --- a/drivers/firmware/efi/memattr.c +++ b/drivers/firmware/efi/memattr.c @@ -94,7 +94,7 @@ static bool entry_is_valid(const efi_memory_desc_t *in, efi_memory_desc_t *out) if (!(md->attribute & EFI_MEMORY_RUNTIME)) continue; - if (md->virt_addr == 0) { + if (md->virt_addr == 0 && md->phys_addr != 0) { /* no virtual mapping has been installed by the stub */ break; } -- cgit v1.2.3-59-g8ed1b