linux-kernel - [PATCH] kasan: disable kasan_non_canonical

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Message-Id: <20231016200925.984439-1-arnd@kernel.org>
Date:   Mon, 16 Oct 2023 22:08:38 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Haibo Li <haibo.li@...iatek.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Kees Cook <keescook@...omium.org>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH] kasan: disable kasan_non_canonical_hook() for HW tags

From: Arnd Bergmann <arnd@...db.de>

On arm64, building with CONFIG_KASAN_HW_TAGS now causes a compile-time
error:

mm/kasan/report.c: In function 'kasan_non_canonical_hook':
mm/kasan/report.c:637:20: error: 'KASAN_SHADOW_OFFSET' undeclared (first use in this function)
  637 |         if (addr < KASAN_SHADOW_OFFSET)
      |                    ^~~~~~~~~~~~~~~~~~~
mm/kasan/report.c:637:20: note: each undeclared identifier is reported only once for each function it appears in
mm/kasan/report.c:640:77: error: expected expression before ';' token
  640 |         orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;

This was caused by removing the dependency on CONFIG_KASAN_INLINE that
used to prevent this from happening. Use the more specific dependency
on KASAN_SW_TAGS || KASAN_GENERIC to only ignore the function for hwasan
mode.

Fixes: 12ec6a919b0f ("kasan: print the original fault addr when access invalid shadow")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
It looks like the comment above the function needs to be adjusted
as well, and it's possible we should still provide it even for
hwasan but fix it in a different way.

I saw this a few days ago but didn't actually send the patch right away, so there
is a good chance that someone has already produced a better patch, just ignore
my report in that case.
---
 include/linux/kasan.h | 6 +++---
 mm/kasan/report.c     | 4 +++-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 485452e8cc0dc..72cb693b075b7 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -468,10 +468,10 @@ static inline void kasan_free_module_shadow(const struct vm_struct *vm) {}
 
 #endif /* (CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS) && !CONFIG_KASAN_VMALLOC */
 
-#ifdef CONFIG_KASAN
+#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 void kasan_non_canonical_hook(unsigned long addr);
-#else /* CONFIG_KASAN */
+#else /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
 static inline void kasan_non_canonical_hook(unsigned long addr) { }
-#endif /* CONFIG_KASAN */
+#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
 
 #endif /* LINUX_KASAN_H */
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index b738be3b6e5cc..e77facb629007 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -621,8 +621,9 @@ void kasan_report_async(void)
 }
 #endif /* CONFIG_KASAN_HW_TAGS */
 
+#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 /*
- * With CONFIG_KASAN, accesses to bogus pointers (outside the high
+ * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
  * canonical half of the address space) cause out-of-bounds shadow memory reads
  * before the actual access. For addresses in the low canonical half of the
  * address space, as well as most non-canonical addresses, that out-of-bounds
@@ -658,3 +659,4 @@ void kasan_non_canonical_hook(unsigned long addr)
 	pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
 		 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
 }
+#endif
-- 
2.39.2