[patch 21/29] kasan: fix KASAN_STACK dependency for HW_TAGS

From: Andrey Konovalov <redacted>
Subject: kasan: fix KASAN_STACK dependency for HW_TAGS

There's a runtime failure when running HW_TAGS-enabled kernel built with
GCC on hardware that doesn't support MTE.  GCC-built kernels always have
CONFIG_KASAN_STACK enabled, even though stack instrumentation isn't
supported by HW_TAGS.  Having that config enabled causes KASAN to issue
MTE-only instructions to unpoison kernel stacks, which causes the failure.

Fix the issue by disallowing CONFIG_KASAN_STACK when HW_TAGS is used.

(The commit that introduced CONFIG_KASAN_HW_TAGS specified proper
 dependency for CONFIG_KASAN_STACK_ENABLE but not for CONFIG_KASAN_STACK.)

Link: https://lkml.kernel.org/r/59e75426241dbb5611277758c8d4d6f5f9298dac.1615215441.git.andreyknvl@google.com
Fixes: 6a63a63ff1ac ("kasan: introduce CONFIG_KASAN_HW_TAGS")
Signed-off-by: Andrey Konovalov <redacted>
Reported-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: <redacted>
Cc: Will Deacon <redacted>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <redacted>
Cc: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Peter Collingbourne <redacted>
Cc: Evgenii Stepanov <redacted>
Cc: Branislav Rankov <redacted>
Cc: Kevin Brodsky <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/Kconfig.kasan |    1 +
 1 file changed, 1 insertion(+)

--- a/lib/Kconfig.kasan~kasan-fix-kasan_stack-dependency-for-hw_tags
+++ a/lib/Kconfig.kasan

@@ -156,6 +156,7 @@ config KASAN_STACK_ENABLE
 
 config KASAN_STACK
 	int
+	depends on KASAN_GENERIC || KASAN_SW_TAGS
 	default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
 	default 0
 

_