linux-kernel - Re: [PATCH 0/2] scsi: fix 2 cases of -Wfortify-source

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Date:   Tue, 29 Aug 2023 11:48:45 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Tom Rix <trix@...hat.com>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Ard Biesheuvel <ardb@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Hannes Reinecke <hare@...nel.org>
Subject: Re: [PATCH 0/2] scsi: fix 2 cases of -Wfortify-source

On Tue, Aug 29, 2023 at 09:33:55AM -0700, Nick Desaulniers wrote:
> On Mon, Aug 28, 2023 at 4:41 PM Nick Desaulniers
> <ndesaulniers@...gle.com> wrote:
> >
> > On Mon, Aug 28, 2023 at 3:25 PM Nick Desaulniers
> > <ndesaulniers@...gle.com> wrote:
> > >
> > > clang-18 has improved its support for detecting operations that will
> > > truncate values at runtime via -wfortify-source resulting in two new
> >
> > ^ -Wfortify-source
> >
> > > warnings (or errors with CONFIG_WERROR=y):
> > >
> > >   drivers/scsi/myrb.c:1906:10: warning: 'snprintf' will always be
> > >   truncated; specified size is 32, but format string expands to at least
> > >   34 [-Wfortify-source]
> > >
> > >   drivers/scsi/myrs.c:1089:10: warning: 'snprintf' will always be
> > >   truncated; specified size is 32, but format string expands to at least
> > >   34 [-Wfortify-source]

These should just use sysfs_emit() instead. Then all the bounds checking
against the PAGE_SIZE buffer gets done correctly, etc.

-- 
Kees Cook