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In-Reply-To: <fe78d723ba64456d68754a944fa93fe4a25c730f.1605046192.git.andreyknvl@google.com>
From:   Alexander Potapenko <glider@google.com>
Date:   Wed, 11 Nov 2020 17:43:19 +0100
Message-ID: <CAG_fn=VkuY7+oDOLWZEvvbxFw6Gduq-XK5r_dn7sEkmYqJA-tA@mail.gmail.com>
Subject: Re: [PATCH v9 40/44] kasan, arm64: print report from tag fault handler
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, Nov 10, 2020 at 11:12 PM 'Andrey Konovalov' via kasan-dev
<kasan-dev@googlegroups.com> wrote:
>
> Add error reporting for hardware tag-based KASAN. When CONFIG_KASAN_HW_TA=
GS
> is enabled, print KASAN report from the arm64 tag fault handler.
>
> SAS bits aren't set in ESR for all faults reported in EL1, so it's
> impossible to find out the size of the access the caused the fault.
> Adapt KASAN reporting code to handle this case.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>

> ---
> Change-Id: I3780fe7db6e075dff2937d3d8508f55c9322b095
> ---
>  arch/arm64/mm/fault.c | 14 ++++++++++++++
>  mm/kasan/report.c     | 11 ++++++++---
>  2 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index fbceb14d93b1..7370e822e588 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>
> @@ -297,10 +298,23 @@ static void die_kernel_fault(const char *msg, unsig=
ned 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  =3D ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) !=
=3D 0;
> +
> +       /*
> +        * 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
>
>  static void do_tag_recovery(unsigned long addr, unsigned int esr,
>                            struct pt_regs *regs)
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 8afc1a6ab202..ce06005d4052 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -62,9 +62,14 @@ static void print_error_description(struct kasan_acces=
s_info *info)
>  {
>         pr_err("BUG: KASAN: %s in %pS\n",
>                 get_bug_type(info), (void *)info->ip);
> -       pr_err("%s of size %zu at addr %px by task %s/%d\n",
> -               info->is_write ? "Write" : "Read", info->access_size,
> -               info->access_addr, current->comm, task_pid_nr(current));
> +       if (info->access_size)
> +               pr_err("%s of size %zu at addr %px by task %s/%d\n",
> +                       info->is_write ? "Write" : "Read", info->access_s=
ize,
> +                       info->access_addr, current->comm, task_pid_nr(cur=
rent));
> +       else
> +               pr_err("%s at addr %px by task %s/%d\n",
> +                       info->is_write ? "Write" : "Read",
> +                       info->access_addr, current->comm, task_pid_nr(cur=
rent));
>  }
>
>  static DEFINE_SPINLOCK(report_lock);
> --
> 2.29.2.222.g5d2a92d10f8-goog
>
> --
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--=20
Alexander Potapenko
Software Engineer

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