From: Nick Desaulniers <ndesaulniers@google.com>
To: David.Laight@aculab.com
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
dhowells@redhat.com, Nathan Chancellor <natechancellor@gmail.com>,
Eric Biggers <ebiggers@google.com>,
zohar@linux.vnet.ibm.com, jmorris@namei.org, serge@hallyn.com,
linux-integrity@vger.kernel.org, keyrings@vger.kernel.org,
linux-security-module@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] KEYS: trusted: fix -Wvarags warning
Date: Mon, 15 Oct 2018 21:53:49 +0000 [thread overview]
Message-ID: <CAKwvOdmXVY1iA-VAs-Ns3qVVnMTeU6v4RqxoS2=SJcSeQ23_og@mail.gmail.com> (raw)
In-Reply-To: <0180360cfcb5458d8ff099744e8884d4@AcuMS.aculab.com>
On Mon, Oct 15, 2018 at 2:26 AM David Laight <David.Laight@aculab.com> wrote:
>
> From: ndesaulniers@google.com
> > Sent: 11 October 2018 21:31
> ...
> > by swapping h2 and h3.
> >
> > security/keys/trusted.c:146:17: warning: passing an object that
> > undergoes default
> > argument promotion to 'va_start' has undefined behavior [-Wvarargs]
> > va_start(argp, h3);
> > ^
> > security/keys/trusted.c:126:37: note: parameter of type 'unsigned
> > char' is declared here
> > unsigned char *h2, unsigned char h3, ...)
> > ^
> > Specifically, it seems that both the C90 (4.8.1.1) and C11 (7.16.1.4)
> > standards explicitly call this out as undefined behavior:
>
> I guess that problems arise when all the arguments are stacked
> and va_start/va_arg use naive pointer manipulation.
> In that case &h3 might be 4n+3 aligned so va_arg() will access
> misaligned stack locations.
>
> I doubt any modern compilers (where va_start and va_arg are builtins)
> will get this 'wrong' even when all arguments are stacked.
>
> Seems clang is being over cautious.
Yes; did you have feedback on the Denis' proposed fix, or another?
>
> David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
--
Thanks,
~Nick Desaulniers
WARNING: multiple messages have this Message-ID (diff)
From: Nick Desaulniers <ndesaulniers@google.com>
To: David.Laight@aculab.com
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
dhowells@redhat.com, Nathan Chancellor <natechancellor@gmail.com>,
Eric Biggers <ebiggers@google.com>,
zohar@linux.vnet.ibm.com, jmorris@namei.org, serge@hallyn.com,
linux-integrity@vger.kernel.org, keyrings@vger.kernel.org,
linux-security-module@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] KEYS: trusted: fix -Wvarags warning
Date: Mon, 15 Oct 2018 14:53:49 -0700 [thread overview]
Message-ID: <CAKwvOdmXVY1iA-VAs-Ns3qVVnMTeU6v4RqxoS2=SJcSeQ23_og@mail.gmail.com> (raw)
In-Reply-To: <0180360cfcb5458d8ff099744e8884d4@AcuMS.aculab.com>
On Mon, Oct 15, 2018 at 2:26 AM David Laight <David.Laight@aculab.com> wrote:
>
> From: ndesaulniers@google.com
> > Sent: 11 October 2018 21:31
> ...
> > by swapping h2 and h3.
> >
> > security/keys/trusted.c:146:17: warning: passing an object that
> > undergoes default
> > argument promotion to 'va_start' has undefined behavior [-Wvarargs]
> > va_start(argp, h3);
> > ^
> > security/keys/trusted.c:126:37: note: parameter of type 'unsigned
> > char' is declared here
> > unsigned char *h2, unsigned char h3, ...)
> > ^
> > Specifically, it seems that both the C90 (4.8.1.1) and C11 (7.16.1.4)
> > standards explicitly call this out as undefined behavior:
>
> I guess that problems arise when all the arguments are stacked
> and va_start/va_arg use naive pointer manipulation.
> In that case &h3 might be 4n+3 aligned so va_arg() will access
> misaligned stack locations.
>
> I doubt any modern compilers (where va_start and va_arg are builtins)
> will get this 'wrong' even when all arguments are stacked.
>
> Seems clang is being over cautious.
Yes; did you have feedback on the Denis' proposed fix, or another?
>
> David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2018-10-15 21:53 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-09 22:11 undefined behavior (-Wvarargs) in security/keys/trusted.c#TSS_authhmac() Nick Desaulniers
2018-10-09 22:11 ` Nick Desaulniers
2018-10-11 16:02 ` Arnd Bergmann
2018-10-11 16:02 ` Arnd Bergmann
2018-10-11 16:10 ` James Bottomley
2018-10-11 16:10 ` James Bottomley
2018-10-11 20:31 ` [PATCH] KEYS: trusted: fix -Wvarags warning ndesaulniers
2018-10-11 20:31 ` ndesaulniers
2018-10-12 1:50 ` Nathan Chancellor
2018-10-12 1:50 ` Nathan Chancellor
2018-10-12 16:55 ` Nick Desaulniers
2018-10-12 16:55 ` Nick Desaulniers
2018-10-12 17:03 ` Nathan Chancellor
2018-10-12 17:03 ` Nathan Chancellor
2018-10-12 12:29 ` Denis Kenzior
2018-10-12 12:29 ` Denis Kenzior
2018-10-12 15:05 ` James Bottomley
2018-10-12 15:05 ` James Bottomley
2018-10-12 15:13 ` Denis Kenzior
2018-10-12 15:13 ` Denis Kenzior
2018-10-12 15:22 ` James Bottomley
2018-10-12 15:22 ` James Bottomley
2018-10-12 15:44 ` Denis Kenzior
2018-10-12 15:44 ` Denis Kenzior
2018-10-12 15:46 ` James Bottomley
2018-10-12 15:46 ` James Bottomley
2018-10-12 15:53 ` Denis Kenzior
2018-10-12 15:53 ` Denis Kenzior
2018-10-12 16:01 ` James Bottomley
2018-10-12 16:01 ` James Bottomley
2018-10-12 17:14 ` Nick Desaulniers
2018-10-12 17:14 ` Nick Desaulniers
2018-10-12 15:25 ` James Bottomley
2018-10-12 15:25 ` James Bottomley
2018-10-12 17:05 ` Nick Desaulniers
2018-10-12 17:05 ` Nick Desaulniers
2018-10-12 17:17 ` Nick Desaulniers
2018-10-12 17:17 ` Nick Desaulniers
2018-10-12 17:27 ` Denis Kenzior
2018-10-12 17:27 ` Denis Kenzior
2018-10-12 18:39 ` Nick Desaulniers
2018-10-12 18:39 ` Nick Desaulniers
2018-10-12 17:02 ` Nick Desaulniers
2018-10-12 17:02 ` Nick Desaulniers
2018-10-12 17:15 ` Denis Kenzior
2018-10-12 17:15 ` Denis Kenzior
2018-10-15 9:26 ` David Laight
2018-10-15 9:26 ` David Laight
2018-10-15 9:26 ` David Laight
2018-10-15 21:53 ` Nick Desaulniers [this message]
2018-10-15 21:53 ` Nick Desaulniers
2018-10-16 8:13 ` David Laight
2018-10-16 8:13 ` David Laight
2018-10-16 8:13 ` David Laight
2018-10-22 23:43 ` [PATCH v2] " ndesaulniers
2018-10-22 23:43 ` ndesaulniers
2018-10-23 0:00 ` Nathan Chancellor
2018-10-23 0:00 ` Nathan Chancellor
2018-10-24 8:36 ` Jarkko Sakkinen
2018-10-24 8:36 ` Jarkko Sakkinen
2018-10-29 17:54 ` Nick Desaulniers
2018-10-29 17:54 ` Nick Desaulniers
2019-02-11 18:36 ` Nick Desaulniers
2019-02-11 18:36 ` Nick Desaulniers
2019-02-12 23:12 ` Jarkko Sakkinen
2019-02-12 23:12 ` Jarkko Sakkinen
2019-02-14 10:52 ` Jarkko Sakkinen
2019-02-14 10:52 ` Jarkko Sakkinen
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