[v3,16/24] x86/boot: Reduce lower limit of physical KASLR

Commit Message

Evgeniy Baskov Nov. 22, 2022, 11:12 a.m. UTC

Set lower limit of physical KASLR to 64M.

Previously is was set to 512M when kernel is loaded higher than that.
That prevented physical KASLR from being performed on x86_32, where
upper limit is also set to 512M. The limit is pretty arbitrary, and the
most important is to set it above the ISA hole, i.e. higher than 16M.

It was not that important before, but now kernel is not getting
relocated to the lower address when booting via EFI, exposing the
KASLR failures.

Tested-by: Mario Limonciello <[e-mail]>
Signed-off-by: Evgeniy Baskov <[e-mail]>
---
 arch/x86/boot/compressed/kaslr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 7e09d65f7b57..672550686f62 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -852,10 +852,10 @@  void choose_random_location(unsigned long input,
 
 	/*
 	 * Low end of the randomization range should be the
-	 * smaller of 512M or the initial kernel image
+	 * smaller of 64M or the initial kernel image
 	 * location:
 	 */
-	min_addr = min(*output, 512UL << 20);
+	min_addr = min(*output, 64UL << 20);
 	/* Make sure minimum is aligned. */
 	min_addr = ALIGN(min_addr, CONFIG_PHYSICAL_ALIGN);