Re: [PATCH mm 06/22] kasan: simplify async check in end_report

[Alexander Potapenko <glider@xxxxxxxxxx>]

On Wed, Mar 2, 2022 at 5:37 PM <andrey.konovalov@xxxxxxxxx> wrote:

From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Currently, end_report() does not call trace_error_report_end() for bugs
detected in either async or asymm mode (when kasan_async_fault_possible()
returns true), as the address of the bad access might be unknown.

However, for asymm mode, the address is known for faults triggered by
read operations.

Instead of using kasan_async_fault_possible(), simply check that
the addr is not NULL when calling trace_error_report_end().

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
 mm/kasan/report.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index d60ee8b81e2b..2d892ec050be 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -112,7 +112,7 @@ static void start_report(unsigned long *flags)

 static void end_report(unsigned long *flags, unsigned long addr)
 {
-       if (!kasan_async_fault_possible())
+       if (addr)
                trace_error_report_end(ERROR_DETECTOR_KASAN, addr);

What happens in the case of a NULL dereference? Don't we want to trigger the tracepoint as well?

--

Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

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