linux-kernel - Re: BUG : PowerPC RCU: torture test failed with __stack_chk

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: <20230424172900.GR19790@gate.crashing.org>
Date:   Mon, 24 Apr 2023 12:29:00 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Joel Fernandes <joel@...lfernandes.org>,
        Zhouyi Zhou <zhouzhouyi@...il.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        rcu <rcu@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, lance@...osl.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: BUG : PowerPC RCU: torture test failed with __stack_chk_fail

On Mon, Apr 24, 2023 at 08:28:55AM -0700, Boqun Feng wrote:
> On Mon, Apr 24, 2023 at 10:13:51AM -0500, Segher Boessenkool wrote:
> > At what points can r13 change?  Only when some particular functions are
> > called?
> 
> r13 is the local paca:
> 
> 	register struct paca_struct *local_paca asm("r13");
> 
> , which is a pointer to percpu data.

Yes, it is a global register variable.

> So if a task schedule from one CPU to anotehr CPU, the value gets
> changed.

But the compiler does not see that something else changes local_paca (or
r13 some other way, via assembler code perhaps)?  Or is there a compiler
bug?

If the latter is true:

Can you make a reproducer and open a GCC PR?  <https://gcc.gnu.org/bugs/>
for how to get started doing that.  We need *exact* code that shows the
problem, together with a compiler command line.  So that we can
reproduce the problem.  That is step 0 in figuring out what is going on,
and then maybe fixing the problem :-)

Segher