netdev - RE: [PATCH net-next v3 1/7] overflow: add DEFINE

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: <8c5fcd66086a4354b30f15dd488a9fe5@AcuMS.aculab.com>
Date: Fri, 18 Aug 2023 10:49:59 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Przemek Kitszel' <przemyslaw.kitszel@...el.com>, 'Kees Cook'
	<keescook@...omium.org>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>, Jacob Keller
	<jacob.e.keller@...el.com>, "intel-wired-lan@...ts.osuosl.org"
	<intel-wired-lan@...ts.osuosl.org>, Alexander Lobakin
	<aleksander.lobakin@...el.com>, "linux-hardening@...r.kernel.org"
	<linux-hardening@...r.kernel.org>, Steven Zou <steven.zou@...el.com>
Subject: RE: [PATCH net-next v3 1/7] overflow: add DEFINE_FLEX() for on-stack
 allocs

From: Przemek Kitszel
> Sent: Friday, August 18, 2023 11:28 AM
...
> >>> I'm not sure you should be forcing the memset() either.
> >>
> >> This already got discussed: better to fail safe.
> >
> > Perhaps call it DEFINE_FLEX_Z() to make this clear and
> > give the option for a non-zeroing version later.
> > Not everyone wants the expense of zeroing everything.
> 
> per Kees, zeroing should be removed by compiler when not needed:
> https://lore.kernel.org/intel-wired-lan/202308101128.C4F0FA235@keescook/

Expect in the most trivial cases the compiler is pretty much never
going to remove the zeroing of the data[] part.

I'm also not at all sure what happens if there is a function
call between the initialisation and any assignments.

With a bit of effort you should be able to pass the '= {}'
through into an inner #define.
Possibly with the alternative of a caller-provider
 '= { .obj = call_supplied_initialiser }'
The 'not _Z' form would pass an empty argument.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)