From: Reinoud Koornstra <reinoudkoornstra@gmail.com>
To: Xi Ruoyao <xry111@mengyan1223.wang>
Cc: Florian Weimer <fweimer@redhat.com>,
Reinoud Koornstra via Gcc-help <gcc-help@gcc.gnu.org>
Subject: Re: Fortify_source and stack-protector-strong
Date: Wed, 2 Mar 2022 12:45:46 -0800 [thread overview]
Message-ID: <CAAA5faG2-YHk1Ae7TaUFnsPoaiPANK_nB3NfOw_R9nbS2po0zw@mail.gmail.com> (raw)
In-Reply-To: <204cd10c9d34c6c798e701f1d990c120c2d77897.camel@mengyan1223.wang>
Thanks for the explanation!
Better to use =2 then.
But Strack protector and FORTIFY can be active as compiler arguments at the
same time as I understand. Just the binary size will grow. Thanks,
Reinoud.
On Wed, Mar 2, 2022, 12:23 PM Xi Ruoyao <xry111@mengyan1223.wang> wrote:
> On Wed, 2022-03-02 at 12:05 -0800, Reinoud Koornstra wrote:
> > Hi Xi,
> >
> > Thanks for your reply.
> > Then what is the difference between -D_FORTIFY_SOURCE=1 and
> -D_FORTIFY_SOURCE=2 exactly?
>
> -D_FORTIFY_SOURCE=1 uses __builtin_object_size(..., 0) as the buffer
> size, but -D_FORTIFY_SOURCE=2 uses __builtin_object_size(..., 1). Read
> https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html for the
> details.
>
> One case is:
>
> struct frame
> {
> int size;
> char buf[0];
> };
>
> union
> {
> struct frame f;
> char padding[100 + sizeof(struct frame)];
> } u;
>
> u.frame.size = strlen(s) + 1;
> strcpy(u.frame.buf, s);
>
> -D_FORTIFY_SOURCE=2 will abort this, but -D_FORTIFY_SOURCE=1 won't.
> (Yes, I know "char buf[0]" should be changed to a flexible array member
> "char buf[]" to fix this, but it is just an example.)
> --
> Xi Ruoyao <xry111@mengyan1223.wang>
> School of Aerospace Science and Technology, Xidian University
>
next prev parent reply other threads:[~2022-03-02 20:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-01 23:23 Reinoud Koornstra
2022-03-02 10:22 ` Florian Weimer
2022-03-02 19:09 ` Reinoud Koornstra
2022-03-02 19:46 ` Xi Ruoyao
2022-03-02 20:05 ` Reinoud Koornstra
2022-03-02 20:23 ` Xi Ruoyao
2022-03-02 20:45 ` Reinoud Koornstra [this message]
2022-03-11 19:01 ` Reinoud Koornstra
2022-03-12 8:19 ` Xi Ruoyao
2022-04-19 11:24 ` Florian Weimer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAAA5faG2-YHk1Ae7TaUFnsPoaiPANK_nB3NfOw_R9nbS2po0zw@mail.gmail.com \
--to=reinoudkoornstra@gmail.com \
--cc=fweimer@redhat.com \
--cc=gcc-help@gcc.gnu.org \
--cc=xry111@mengyan1223.wang \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).