linux-kernel - Re: [PATCH v2 34/37] kasan, arm64: print report from tag fault handler

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Message-ID: <CAAeHK+zLzajA8-TTJ4OjoMtgPB=hyJRxzz7WwG4gc=tHTuB3Yw@mail.gmail.com>
Date:   Fri, 18 Sep 2020 14:26:43 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 34/37] kasan, arm64: print report from tag fault handler

On Thu, Sep 17, 2020 at 7:04 PM Catalin Marinas <catalin.marinas@....com> wrote:
>
> On Tue, Sep 15, 2020 at 11:16:16PM +0200, Andrey Konovalov wrote:
> > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> > index cdc23662691c..ac79819317f2 100644
> > --- a/arch/arm64/mm/fault.c
> > +++ b/arch/arm64/mm/fault.c
> > @@ -14,6 +14,7 @@
> >  #include <linux/mm.h>
> >  #include <linux/hardirq.h>
> >  #include <linux/init.h>
> > +#include <linux/kasan.h>
> >  #include <linux/kprobes.h>
> >  #include <linux/uaccess.h>
> >  #include <linux/page-flags.h>
> > @@ -295,17 +296,23 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
> >       do_exit(SIGKILL);
> >  }
> >
> > +#ifdef CONFIG_KASAN_HW_TAGS
> >  static void report_tag_fault(unsigned long addr, unsigned int esr,
> >                            struct pt_regs *regs)
> >  {
> > -     bool is_write = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
> > +     bool is_write  = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
> >
> > -     pr_alert("Memory Tagging Extension Fault in %pS\n", (void *)regs->pc);
> > -     pr_alert("  %s at address %lx\n", is_write ? "Write" : "Read", addr);
> > -     pr_alert("  Pointer tag: [%02x], memory tag: [%02x]\n",
> > -                     mte_get_ptr_tag(addr),
> > -                     mte_get_mem_tag((void *)addr));
> > +     /*
> > +      * SAS bits aren't set for all faults reported in EL1, so we can't
> > +      * find out access size.
> > +      */
> > +     kasan_report(addr, 0, is_write, regs->pc);
> >  }
> > +#else
> > +/* Tag faults aren't enabled without CONFIG_KASAN_HW_TAGS. */
> > +static inline void report_tag_fault(unsigned long addr, unsigned int esr,
> > +                                 struct pt_regs *regs) { }
> > +#endif
>
> So is there a point in introducing this function in an earlier patch,
> just to remove its content here?

I added it to make the first patch somewhat self-consistent. But we
can drop it in v3 if you think it's not needed.