linux-kernel - Re: linux-next: Tree for Oct 18 (objtool)

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Message-ID: <20191021193652.lfccehm37dkkofp7@wittgenstein>
Date:   Mon, 21 Oct 2019 21:36:53 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, linux@...musvillemoes.dk,
        cyphar@...har.com, keescook@...omium.org
Subject: Re: linux-next: Tree for Oct 18 (objtool)

On Mon, Oct 21, 2019 at 03:47:59PM +0200, Peter Zijlstra wrote:
> On Mon, Oct 21, 2019 at 03:19:48PM +0200, Christian Brauner wrote:
> > On Mon, Oct 21, 2019 at 03:11:49PM +0200, Peter Zijlstra wrote:
> 
> > > By popular request; here's that alternative. Completely untested :-)
> > 
> > Am I not getting some mails? :)
> 
> You're not on the 'right' IRC channels :-)

Well, we saw that that wasn't true today. :)

> 
> > I prefer this one as it allows us to avoid working around this in
> > usercopy.c. Should especially make if this potentially helps in other
> > cases as well?
> 
> That was Josh's argument too.
> 
> Personally I think GCC is being a moron here, because with value range
> analysis it should be able to prove the shift-UB cannot happen (the <
> sizeof(unsigned long) conditions on both), but alas, it emits the UBSAN
> calls anyway.

Ok, so I take it you route that patch somehwere through tip?
I'm happy with the ubsan fix:

Acked-by: Christian Brauner <christian.brauner@...ntu.com>