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From:   Andrey Konovalov <andreyknvl@gmail.com>
Date:   Fri, 18 Feb 2022 16:07:58 +0100
Message-ID: <CA+fCnZfAwSJQp7zE+qHChaSvy1uEL6xi0JiHtMi6iq29Fk3tRw@mail.gmail.com>
Subject: Re: [PATCH mm] kasan: print virtual mapping info in reports
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     andrey.konovalov@linux.dev, Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrey Konovalov <andreyknvl@google.com>
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On Thu, Feb 17, 2022 at 1:00 PM Mark Rutland <mark.rutland@arm.com> wrote:
>
> On Wed, Feb 16, 2022 at 08:01:37PM +0100, andrey.konovalov@linux.dev wrote:
> > From: Andrey Konovalov <andreyknvl@google.com>
> >
> > Print virtual mapping range and its creator in reports affecting virtual
> > mappings.
> >
> > Also get physical page pointer for such mappings, so page information
> > gets printed as well.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> >
> > ---
> >
> > Note: no need to merge this patch into any of the KASAN vmalloc patches
> > that are already in mm, better to keep it separate.
> > ---
> >  mm/kasan/report.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > index 137c2c0b09db..8002fb3c417d 100644
> > --- a/mm/kasan/report.c
> > +++ b/mm/kasan/report.c
> > @@ -260,8 +260,18 @@ static void print_address_description(void *addr, u8 tag)
> >               pr_err(" %pS\n", addr);
> >       }
> >
> > +     if (is_vmalloc_addr(addr)) {
> > +             struct vm_struct *va = find_vm_area(addr);
> > +
> > +             pr_err("The buggy address belongs to the virtual mapping at\n"
> > +                    " [%px, %px) created by:\n"
> > +                    " %pS\n", va->addr, va->addr + va->size, va->caller);
>
> The return value of find_vm_area() needs a NULL check here;
> is_vmalloc_addr(addr) just checks that `addr` is within the vmalloc VA
> range, and doesn't guarantee that there is a vmap_area associated with
> that `addr`.
>
> Without the NULL-check, we'll blow up on the `va->addr` dereference and
> will fail to make the report, which would be unfortunate.

Indeed. Will fix in v2. Thanks, Mark!