Commit ef8923e6 authored Jul 04, 2025 by Breno Leitao Committed by Will Deacon Jul 04, 2025

arm64: efi: Fix KASAN false positive for EFI runtime stack

KASAN reports invalid accesses during arch_stack_walk() for EFI runtime
services due to vmalloc tagging[1]. The EFI runtime stack must be allocated
with KASAN tags reset to avoid false positives.

This patch uses arch_alloc_vmap_stack() instead of __vmalloc_node() for
EFI stack allocation, which internally calls kasan_reset_tag()

The changes ensure EFI runtime stacks are properly sanitized for KASAN
while maintaining functional consistency.

Link: https://lore.kernel.org/all/aFVVEgD0236LdrL6@gmail.com/

 [1]
Suggested-by: Andrey Konovalov <andreyknvl@gmail.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20250704-arm_kasan-v2-1-32ebb4fd7607@debian.org


Signed-off-by: Will Deacon <will@kernel.org>

parent 39dfc971

arch/arm64/kernel/efi.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -15,6 +15,7 @@

		#include <asm/efi.h>
		#include <asm/stacktrace.h>
		#include <asm/vmap_stack.h>

		static bool region_is_misaligned(const efi_memory_desc_t *md)
		{
		@@ -214,9 +215,13 @@ static int __init arm64_efi_rt_init(void)
		if (!efi_enabled(EFI_RUNTIME_SERVICES))
		return 0;

		p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
		NUMA_NO_NODE, &&l);
		l: if (!p) {
		if (!IS_ENABLED(CONFIG_VMAP_STACK)) {
		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
		return -ENOMEM;
		}

		p = arch_alloc_vmap_stack(THREAD_SIZE, NUMA_NO_NODE);
		if (!p) {
		pr_warn("Failed to allocate EFI runtime stack\n");
		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
		return -ENOMEM;