Messages in this thread | | | From | Andrey Konovalov <> | Date | Tue, 8 Mar 2022 15:09:33 +0100 | Subject | Re: [PATCH mm 06/22] kasan: simplify async check in end_report |
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On Wed, Mar 2, 2022 at 6:38 PM Alexander Potapenko <glider@google.com> wrote: > > > > On Wed, Mar 2, 2022 at 5:37 PM <andrey.konovalov@linux.dev> wrote: >> >> From: Andrey Konovalov <andreyknvl@google.com> >> >> 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@google.com> >> --- >> 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?
A NULL pointer dereference is never reported through KASAN: for software modes, it triggers a GPF when accessing shadow, and for HW_TAGS, it takes precedence over a tag mismatch.
Thanks!
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