From: Ard Biesheuvel ard.biesheuvel@linaro.org
[ Upstream commit 5de0fef0230f3c8d75cff450a71740a7bf2db866 ]
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 ard.biesheuvel@linaro.org Acked-by: Sai Praneeth Prakhya sai.praneeth.prakhya@intel.com Cc: AKASHI Takahiro takahiro.akashi@linaro.org Cc: Alexander Graf agraf@suse.de Cc: Bjorn Andersson bjorn.andersson@linaro.org Cc: Borislav Petkov bp@alien8.de Cc: Heinrich Schuchardt xypron.glpk@gmx.de Cc: Jeffrey Hugo jhugo@codeaurora.org Cc: Lee Jones lee.jones@linaro.org Cc: Leif Lindholm leif.lindholm@linaro.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matt Fleming matt@codeblueprint.co.uk Cc: Peter Jones pjones@redhat.com Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de 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 mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/firmware/efi/memattr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
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; }