From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: syzbot <syzbot+84fe685c02cd112a2ac3@syzkaller.appspotmail.com>,
bp@alien8.de, hpa@zytor.com, inglorion@google.com,
linux-kernel@vger.kernel.org, mingo@redhat.com,
syzkaller-bugs@googlegroups.com, tglx@linutronix.de,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [syzbot] KASAN: stack-out-of-bounds Read in profile_pc
Date: Thu, 3 Jun 2021 08:29:58 -0500 [thread overview]
Message-ID: <20210603132958.3es4xagwdijmzpqh@treble> (raw)
In-Reply-To: <527ad07e-eec2-a211-03e7-afafe5196100@linux.intel.com>
On Wed, Jun 02, 2021 at 04:35:11PM -0700, Andi Kleen wrote:
>
> > profile_pc() assumes the return address is either directly at regs->sp,
> > or one word adjacent to it due to saved flags, both of which are just
> > completely wrong. This code has probably never worked with ORC, and
> > nobody noticed apparently.
>
> I presume it used to work because the lock functions were really simple, but
> that's not true anymore.
Yeah, I figured as much.
> > We could just use ORC to unwind to the next frame. Though, isn't
> > /proc/profile redundant, compared to all the more sophisticated options
> > nowadays? Is there still a distinct use case for it or can we just
> > remove it?
>
> It's still needed for some special cases. For example there is no other
> viable way to profile early boot without a VM
>
> I would just drop the hack to unwind, at least for the early boot profile
> use case locking profiling is usually not needed.
Ok, I'll just get rid of the hack then.
--
Josh
next prev parent reply other threads:[~2021-06-03 13:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-31 7:15 [syzbot] KASAN: stack-out-of-bounds Read in profile_pc syzbot
2021-06-02 23:00 ` Josh Poimboeuf
2021-06-02 23:35 ` Andi Kleen
2021-06-03 13:29 ` Josh Poimboeuf [this message]
2021-06-03 13:30 ` Peter Zijlstra
2021-06-03 13:39 ` Josh Poimboeuf
2021-06-03 13:52 ` Andi Kleen
2021-10-11 13:07 ` Lee Jones
2021-10-11 14:43 ` Steven Rostedt
2021-10-11 17:10 ` Dmitry Vyukov
2021-10-11 17:30 ` Josh Poimboeuf
2021-06-03 8:02 ` syzbot
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