From 77a1f6883dc6e837bb2cb30b9b02e2f94338e2c6 Mon Sep 17 00:00:00 2001 From: Karl Mehltretter Date: Sun, 24 May 2026 06:52:35 +0100 Subject: [PATCH] ARM: 9475/1: entry: use byte load for KASAN VMAP stack shadow Commit 44e9a3bb76e5 ("ARM: 9430/1: entry: Do a dummy read from VMAP shadow") added a dummy read from the KASAN VMAP stack shadow in __switch_to(). The read uses ldr, but the KASAN shadow address is byte-granular and is not guaranteed to be word aligned. ARMv5 faults unaligned word loads. With CONFIG_KASAN_VMALLOC and CONFIG_VMAP_STACK enabled, ARM926/VersatilePB crashes in __switch_to() with an alignment exception before reaching init. Use ldrb for the dummy shadow access. The code only needs to fault in the shadow mapping if the stack shadow is missing, so a byte load is sufficient and matches the granularity of KASAN shadow memory. Fixes: 44e9a3bb76e5 ("ARM: 9430/1: entry: Do a dummy read from VMAP shadow") Cc: stable@vger.kernel.org # v6.13+ Signed-off-by: Karl Mehltretter Reviewed-by: Linus Walleij Signed-off-by: Russell King --- arch/arm/kernel/entry-armv.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index ef6a657c8d13..a3d050ce9b79 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -567,7 +567,7 @@ ENTRY(__switch_to) @ are using KASAN mov_l r2, KASAN_SHADOW_OFFSET add r2, r2, ip, lsr #KASAN_SHADOW_SCALE_SHIFT - ldr r2, [r2] + ldrb r2, [r2] #endif #endif