linux-kernel - Re: [PATCH 05/10] efi/libstub: distinguish between native/mixed not 32/64 bit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20191214194936.GB140998@rani.riverdale.lan>
Date:   Sat, 14 Dec 2019 14:49:36 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Arvind Sankar <nivedita@...m.mit.edu>
Cc:     Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org,
        linux-efi@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
        Matthew Garrett <matthewgarrett@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 05/10] efi/libstub: distinguish between native/mixed not
 32/64 bit

On Sat, Dec 14, 2019 at 02:46:27PM -0500, Arvind Sankar wrote:
> On Sat, Dec 14, 2019 at 06:57:30PM +0100, Ard Biesheuvel wrote:
> > +
> > +#define efi_table_attr(table, attr, instance) ({			\
> > +	__typeof__(((table##_t *)0)->attr) __ret;			\
> > +	if (efi_is_native()) {						\
> > +		__ret = ((table##_t *)instance)->attr;			\
> > +	} else {							\
> > +		__typeof__(((table##_32_t *)0)->attr) at;		\
> > +		at = (((table##_32_t *)(unsigned long)instance)->attr);	\
> > +		__ret = (__typeof__(__ret))(unsigned long)at;		\
> > +	}								\
> > +	__ret;								\
> > +})
> 
> The casting of `at' is appropriate if the attr is a pointer type which
> needs to be zero-extended to 64-bit, but for other fields it is
> unnecessary at best and possibly dangerous.  There are probably no
> instances currently where it is called for a non-pointer field, but is
> it possible to detect if the type is pointer and avoid the cast if not?

To clarify, I mean the casting via `unsigned long' -- casting to type of
__ret should be ok. We could also use uintptr_t for cleanliness when the
cast is required?