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Date: Fri, 22 Jan 2021 15:46:37 +0100 From: Andrey Konovalov <andreyknvl@...gle.com> To: Vincenzo Frascino <vincenzo.frascino@....com> Cc: Linux ARM <linux-arm-kernel@...ts.infradead.org>, LKML <linux-kernel@...r.kernel.org>, kasan-dev <kasan-dev@...glegroups.com>, Andrey Ryabinin <aryabinin@...tuozzo.com>, Alexander Potapenko <glider@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Leon Romanovsky <leonro@...lanox.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>, "Paul E . McKenney" <paulmck@...nel.org>, Naresh Kamboju <naresh.kamboju@...aro.org> Subject: Re: [PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report() On Fri, Jan 22, 2021 at 3:38 PM Vincenzo Frascino <vincenzo.frascino@....com> wrote: > > With the introduction of KASAN_HW_TAGS, kasan_report() dereferences > the address passed as a parameter. It doesn't dereference the address, it accesses the metadata. And only when addr_has_metadata() succeeds. > > Add a comment to make sure that the preconditions to the function are > explicitly clarified. > > Note: An invalid address (e.g. NULL) passed to the function when, > KASAN_HW_TAGS is enabled, leads to a kernel panic. This is no longer true, right? Commit description needs to be updated. > > Cc: Andrey Ryabinin <aryabinin@...tuozzo.com> > Cc: Alexander Potapenko <glider@...gle.com> > Cc: Dmitry Vyukov <dvyukov@...gle.com> > Cc: Leon Romanovsky <leonro@...lanox.com> > Cc: Andrey Konovalov <andreyknvl@...gle.com> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com> > --- > include/linux/kasan.h | 7 +++++++ > mm/kasan/kasan.h | 2 +- > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index fe1ae73ff8b5..0aea9e2a2a01 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h > @@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr) > return (void *)arch_kasan_reset_tag(addr); > } > > +/** > + * kasan_report - print a report about a bad memory access detected by KASAN > + * @addr: address of the bad access > + * @size: size of the bad access > + * @is_write: whether the bad access is a write or a read > + * @ip: instruction pointer for the accessibility check or the bad access itself > + */ Looks good, thanks! > bool kasan_report(unsigned long addr, size_t size, > bool is_write, unsigned long ip); > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index cc4d9e1d49b1..8c706e7652f2 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, > > static inline bool addr_has_metadata(const void *addr) > { > - return true; > + return (is_vmalloc_addr(addr) || virt_addr_valid(addr)); > } Let's put this change into a separate patch. > > #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ > -- > 2.30.0 >
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