efi/libstub/arm: Don't randomize runtime regions when CONFIG_HIBERNATION=y

38fb6652 · Ard Biesheuvel <[email protected]> · 2017-10-25 11:04:48 +01:00

Commit:

  e69176d68d26 ("ef/libstub/arm/arm64: Randomize the base of the UEFI rt services region")

implemented randomization of the virtual mapping that the OS chooses for
the UEFI runtime services. This was motivated by the fact that UEFI usually
does not bother to specify any permission restrictions for those regions,
making them prime real estate for exploitation now that the OS is getting
more and more careful not to leave any R+W+X mapped regions lying around.

However, this randomization breaks assumptions in the resume from
hibernation code, which expects all memory regions populated by UEFI to
remain in the same place, including their virtual mapping into the OS
memory space. While this assumption may not be entirely reasonable in the
first place, breaking it deliberately does not make a lot of sense either.
So let's refrain from this randomization pass if CONFIG_HIBERNATION=y.

Signed-off-by: Ard Biesheuvel <[email protected]>
Cc: James Morse <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Commit: 38fb6652229c2149e8694d57db442878fdf8a1bd
Parents: 092e72c9

Changes

1 files changed · +2 −1

File	Status	Add	Del	Content
drivers/firmware/efi/libstub/arm-stub.c	modified	+2	−1	View file

drivers/firmware/efi/libstub/arm-stub.c

View file

diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 1cb2d1c..a94601d 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -238,7 +238,8 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
 
 	efi_random_get_seed(sys_table);
 
-	if (!nokaslr()) {
+	/* hibernation expects the runtime regions to stay in the same place */
+	if (!IS_ENABLED(CONFIG_HIBERNATION) && !nokaslr()) {
 		/*
 		 * Randomize the base of the UEFI runtime services region.
 		 * Preserve the 2 MB alignment of the region by taking a