Thread (107 messages) 107 messages, 6 authors, 2020-11-13

Re: [PATCH v9 21/44] kasan: kasan_non_canonical_hook only for software modes

From: Alexander Potapenko <glider@google.com>
Date: 2020-11-12 15:16:45
Also in: linux-mm, lkml

On Wed, Nov 11, 2020 at 7:52 PM 'Andrey Konovalov' via kasan-dev
[off-list ref] wrote:
On Wed, Nov 11, 2020 at 4:09 PM Alexander Potapenko [off-list ref] wrote:
quoted
On Tue, Nov 10, 2020 at 11:11 PM Andrey Konovalov [off-list ref] wrote:
quoted
This is a preparatory commit for the upcoming addition of a new hardware
tag-based (MTE-based) KASAN mode.

kasan_non_canonical_hook() is only applicable to KASAN modes that use
shadow memory, and won't be needed for hardware tag-based KASAN.

No functional changes for software modes.

Signed-off-by: Andrey Konovalov <redacted>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Marco Elver <elver@google.com>
---
Change-Id: Icc9f5ef100a2e86f3a4214a0c3131a68266181b2
---
 mm/kasan/report.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 5d5733831ad7..594bad2a3a5e 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -403,7 +403,8 @@ bool kasan_report(unsigned long addr, size_t size, bool is_write,
        return ret;
 }

-#ifdef CONFIG_KASAN_INLINE
+#if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \
+       defined(CONFIG_KASAN_INLINE)
 /*
  * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
  * canonical half of the address space) cause out-of-bounds shadow memory reads
Perhaps this comment also needs to be updated.
In what way?
Ok, maybe not. I thought you were restricting the set of configs under
which this hook is used, so this should've been explained.
But as far as I understand, CONFIG_KASAN_INLINE already implies
"defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)",
doesn't it?
Maybe this change is not needed at all then?
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-- 
Alexander Potapenko
Software Engineer

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