linux-kernel - Re: [PATCH v3] x86/boot: Warn on future overlapping memcpy() use

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Message-ID: <CAGXu5jJPSP+xzwB7oDoK21Jqumdm+wO4Ki5L1p+Qt9LMBoRjxw@mail.gmail.com>
Date:	Thu, 28 Apr 2016 17:15:11 -0700
From:	Kees Cook <keescook@...omium.org>
To:	kbuild test robot <lkp@...el.com>
Cc:	kbuild-all@...org, LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v3] x86/boot: Warn on future overlapping memcpy() use

Argh. I'm hating this patch. :)

Will fix with v4.

On Thu, Apr 28, 2016 at 4:56 PM, kbuild test robot <lkp@...el.com> wrote:
> Hi,
>
> [auto build test ERROR on tip/auto-latest]
> [cannot apply to tip/x86/core v4.6-rc5 next-20160428]
> [if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
>
> url:    https://github.com/0day-ci/linux/commits/Kees-Cook/x86-boot-Warn-on-future-overlapping-memcpy-use/20160429-075026
> config: i386-tinyconfig (attached as .config)
> reproduce:
>         # save the attached .config to linux build tree
>         make ARCH=i386
>
> All error/warnings (new ones prefixed by >>):
>
>    arch/x86/boot/compressed/string.c: In function 'memmove':
>>> arch/x86/boot/compressed/string.c:56:10: warning: implicit declaration of function 'memcpy' [-Wimplicit-function-declaration]
>       return memcpy(dest, src, n);
>              ^
>>> arch/x86/boot/compressed/string.c:56:10: warning: return makes pointer from integer without a cast [-Wint-conversion]
>    arch/x86/boot/compressed/string.c: At top level:
>>> arch/x86/boot/compressed/string.c:65:7: error: conflicting types for 'memcpy'
>     void *memcpy(void *dest, const void *src, size_t n)
>           ^
>    arch/x86/boot/compressed/string.c:56:10: note: previous implicit declaration of 'memcpy' was here
>       return memcpy(dest, src, n);
>              ^
>    arch/x86/boot/compressed/string.c: In function 'memcpy':
>>> arch/x86/boot/compressed/string.c:68:3: warning: implicit declaration of function 'warn' [-Wimplicit-function-declaration]
>       warn("Avoiding potentially unsafe overlapping memcpy()!");
>       ^
>
> vim +/memcpy +65 arch/x86/boot/compressed/string.c
>
>     50  void *memmove(void *dest, const void *src, size_t n)
>     51  {
>     52          unsigned char *d = dest;
>     53          const unsigned char *s = src;
>     54
>     55          if (d <= s || d - s >= n)
>   > 56                  return memcpy(dest, src, n);
>     57
>     58          while (n-- > 0)
>     59                  d[n] = s[n];
>     60
>     61          return dest;
>     62  }
>     63
>     64  /* Detect and warn about potential overlaps, but handle them with memmove. */
>   > 65  void *memcpy(void *dest, const void *src, size_t n)
>     66  {
>     67          if (dest > src && dest - src < n) {
>   > 68                  warn("Avoiding potentially unsafe overlapping memcpy()!");
>     69                  return memmove(dest, src, n);
>     70          }
>     71          return __memcpy(dest, src, n);
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation



-- 
Kees Cook
Chrome OS & Brillo Security