From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 1/1] seq_file: Replace strncpy()+nul by strscpy()
Date: Wed, 19 Jul 2023 08:26:56 +0300 [thread overview]
Message-ID: <ZLd0IDr+m6hAe4CK@smile.fi.intel.com> (raw)
In-Reply-To: <202307182147.A5B81B67D@keescook>
On Tue, Jul 18, 2023 at 10:00:24PM -0700, Kees Cook wrote:
> On Mon, Jul 17, 2023 at 04:09:23PM -0700, Kees Cook wrote:
> > On Mon, 17 Jul 2023 12:33:32 +0300, Andy Shevchenko wrote:
> > > Privided seq_show_option_n() macro breaks build with -Werror
> > > and W=1, e.g.:
> > >
> > > In function ‘strncpy’,
> > > inlined from ‘ocfs2_show_options’ at fs/ocfs2/super.c:1520:3:
> > > include/linux/fortify-string.h:68:33: error: ‘__builtin_strncpy’ output may be truncated copying 4 bytes from a string of length 4 [-Werror=stringop-truncation]
> > > 68 | #define __underlying_strncpy __builtin_strncpy
> > > | ^
> > > include/linux/fortify-string.h:151:16: note: in expansion of macro ‘__underlying_strncpy’
> > > 151 | return __underlying_strncpy(p, q, size);
> > > | ^~~~~~~~~~~~~~~~~~~~
> > > cc1: all warnings being treated as errors
> > >
> > > [...]
> >
> > Applied, thanks!
> >
> > [1/1] seq_file: Replace strncpy()+nul by strscpy()
> > https://git.kernel.org/kees/c/c30417b20f49
>
> Gah, I dropped this from my tree since it was actually wrong[1]. This is an
> ugly corner case with strscpy vs strncpy: the cast be32 from hfs/hfsplus[2]
> looks unterminated to strscpy, so it would return -E2BIG, but really
> FORTIFY noticed the over-read (strscpy is correctly checking the 5th
> byte for NUL).
>
> So... I think we need to fix seq_show_option_n() using memcpy+NUL, drop
> the ocfs2 usage, and clarify that the seq_show_option_n() docs mean
> "n means _exactly_ n bytes"...
Sounds like a plan!
Please go ahead with that. My intention is to make eventually build kernel with
`make W=1` when CONFIG_WERROR=y.
> [1] https://lore.kernel.org/lkml/0000000000000a88cb0600ccef54@google.com/
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/hfsplus/options.c?h=v6.4#n221
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2023-07-19 5:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-17 9:33 Andy Shevchenko
2023-07-17 15:43 ` Kees Cook
2023-07-17 16:05 ` Andy Shevchenko
2023-07-17 22:58 ` Kees Cook
2023-07-17 23:09 ` Kees Cook
2023-07-19 5:00 ` Kees Cook
2023-07-19 5:26 ` Andy Shevchenko [this message]
2023-07-18 9:42 ` David Laight
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