linux-kernel - Re: [PATCH 2/3] kasan: move kasan

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Date:   Thu, 28 May 2020 17:00:54 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Qian Cai <cai@....pw>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Leon Romanovsky <leonro@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 2/3] kasan: move kasan_report() into report.c

On Thu, May 28, 2020 at 3:49 PM Qian Cai <cai@....pw> wrote:
>
> On Tue, May 12, 2020 at 05:33:20PM +0200, 'Andrey Konovalov' via kasan-dev wrote:
> > The kasan_report() functions belongs to report.c, as it's a common
> > functions that does error reporting.
> >
> > Reported-by: Leon Romanovsky <leon@...nel.org>
> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
>
> Today's linux-next produced this with Clang 11.
>
> mm/kasan/report.o: warning: objtool: kasan_report()+0x8a: call to __stack_chk_fail() with UACCESS enabled
>
> kasan_report at mm/kasan/report.c:536

Hm, the first patch in the series ("kasan: consistently disable
debugging features") disables stack protector for kasan files. Is that
patch in linux-next?

>
> > ---
> >  mm/kasan/common.c | 19 -------------------
> >  mm/kasan/report.c | 22 ++++++++++++++++++++--
> >  2 files changed, 20 insertions(+), 21 deletions(-)
> >
> > diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> > index 2906358e42f0..757d4074fe28 100644
> > --- a/mm/kasan/common.c
> > +++ b/mm/kasan/common.c
> > @@ -33,7 +33,6 @@
> >  #include <linux/types.h>
> >  #include <linux/vmalloc.h>
> >  #include <linux/bug.h>
> > -#include <linux/uaccess.h>
> >
> >  #include <asm/cacheflush.h>
> >  #include <asm/tlbflush.h>
> > @@ -613,24 +612,6 @@ void kasan_free_shadow(const struct vm_struct *vm)
> >  }
> >  #endif
> >
> > -extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);
> > -extern bool report_enabled(void);
> > -
> > -bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
> > -{
> > -     unsigned long flags = user_access_save();
> > -     bool ret = false;
> > -
> > -     if (likely(report_enabled())) {
> > -             __kasan_report(addr, size, is_write, ip);
> > -             ret = true;
> > -     }
> > -
> > -     user_access_restore(flags);
> > -
> > -     return ret;
> > -}
> > -
> >  #ifdef CONFIG_MEMORY_HOTPLUG
> >  static bool shadow_mapped(unsigned long addr)
> >  {
> > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > index 80f23c9da6b0..51ec45407a0b 100644
> > --- a/mm/kasan/report.c
> > +++ b/mm/kasan/report.c
> > @@ -29,6 +29,7 @@
> >  #include <linux/kasan.h>
> >  #include <linux/module.h>
> >  #include <linux/sched/task_stack.h>
> > +#include <linux/uaccess.h>
> >
> >  #include <asm/sections.h>
> >
> > @@ -454,7 +455,7 @@ static void print_shadow_for_address(const void *addr)
> >       }
> >  }
> >
> > -bool report_enabled(void)
> > +static bool report_enabled(void)
> >  {
> >       if (current->kasan_depth)
> >               return false;
> > @@ -479,7 +480,8 @@ void kasan_report_invalid_free(void *object, unsigned long ip)
> >       end_report(&flags);
> >  }
> >
> > -void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
> > +static void __kasan_report(unsigned long addr, size_t size, bool is_write,
> > +                             unsigned long ip)
> >  {
> >       struct kasan_access_info info;
> >       void *tagged_addr;
> > @@ -518,6 +520,22 @@ void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned lon
> >       end_report(&flags);
> >  }
> >
> > +bool kasan_report(unsigned long addr, size_t size, bool is_write,
> > +                     unsigned long ip)
> > +{
> > +     unsigned long flags = user_access_save();
> > +     bool ret = false;
> > +
> > +     if (likely(report_enabled())) {
> > +             __kasan_report(addr, size, is_write, ip);
> > +             ret = true;
> > +     }
> > +
> > +     user_access_restore(flags);
> > +
> > +     return ret;
> > +}
> > +
> >  #ifdef CONFIG_KASAN_INLINE
> >  /*
> >   * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
> > --
> > 2.26.2.645.ge9eca65c58-goog
> >
> > --
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> > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/78a81fde6eeda9db72a7fd55fbc33173a515e4b1.1589297433.git.andreyknvl%40google.com.