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Date:   Wed, 13 May 2020 23:52:10 +0200
From:   Pavel Machek <pavel@denx.de>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Miroslav Benes <mbenes@suse.cz>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Ingo Molnar <mingo@kernel.org>,
        Andy Lutomirski <luto@kernel.org>, Dave Jones <dsj@fb.com>,
        Jann Horn <jannh@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vince Weaver <vincent.weaver@maine.edu>
Subject: Re: [PATCH 4.19 41/48] x86/unwind/orc: Prevent unwinding before ORC
 initialization
Message-ID: <20200513215210.GB27858@amd>
References: <20200513094351.100352960@linuxfoundation.org>
 <20200513094402.645961403@linuxfoundation.org>
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Hi!

> From: Josh Poimboeuf <jpoimboe@redhat.com>
>=20
> commit 98d0c8ebf77e0ba7c54a9ae05ea588f0e9e3f46e upstream.
>=20
> If the unwinder is called before the ORC data has been initialized,
> orc_find() returns NULL, and it tries to fall back to using frame
> pointers.  This can cause some unexpected warnings during boot.
>=20
> Move the 'orc_init' check from orc_find() to __unwind_init(), so that it
> doesn't even try to unwind from an uninitialized state.

> @@ -563,6 +560,9 @@ EXPORT_SYMBOL_GPL(unwind_next_frame);
>  void __unwind_start(struct unwind_state *state, struct task_struct *task,
>  		    struct pt_regs *regs, unsigned long *first_frame)
>  {
> +	if (!orc_init)
> +		goto done;
> +
>  	memset(state, 0, sizeof(*state));
>  	state->task =3D task;
> =20

As this returns the *state to the caller, should the "goto done" move
below the memset? Otherwise we are returning partialy-initialized
struct, which is ... weird.

Best regards,
									Pavel
--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

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