linux-kernel - RE: struct_size() using sizeof() vs offsetof()

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: <d3c4c953c9a742ae98ae9b9036561b38@AcuMS.aculab.com>
Date:   Mon, 21 Aug 2023 08:38:43 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Alejandro Colomar' <alx@...nel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
CC:     LKML <linux-kernel@...r.kernel.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: RE: struct_size() using sizeof() vs offsetof()

From: Alejandro Colomar <alx@...nel.org>
> Sent: Thursday, August 17, 2023 7:38 PM
> 
> Hi Gustavo,
> 
> On 2023-08-17 18:05, Gustavo A. R. Silva wrote:
> >
> >> -               tp_c = kzalloc(sizeof(*tp_c), GFP_KERNEL);
> >> +               tp_c = kzalloc(struct_size(tp_c, hlist->ht, 1), GFP_KERNEL);
> >
> > I just sent a fix[1].
> >
> > Thanks for reporting this! :)

Perhaps struct_size() should include an assertion that:
	(offsetof(type, field[8]) > sizeof (type))
That will ensure that field is an array member and reasonably
near the end of the structure.

A more complex calculation (using _Alignof(type) and the offset/size
of field) could be used.
But I don't think you can actually detect it is field[] (or even the
last member).

	David

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