From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758458Ab2GKXmg (ORCPT ); Wed, 11 Jul 2012 19:42:36 -0400 Received: from na3sys009aog128.obsmtp.com ([74.125.149.141]:56124 "EHLO na3sys009aog128.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754650Ab2GKXmf (ORCPT ); Wed, 11 Jul 2012 19:42:35 -0400 Date: Wed, 11 Jul 2012 16:42:29 -0700 From: Mike Turquette To: Linus Walleij Cc: Mike Turquette , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@kernel.org, Ulf Hansson Subject: Re: [PATCH] clk: allow clocks without parents to change rate Message-ID: <20120711234229.GF2772@gmail.com> References: <1341439772-649-1-git-send-email-linus.walleij@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1341439772-649-1-git-send-email-linus.walleij@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20120705-00:09, Linus Walleij wrote: > The clk_change_rate() code would dereference clk->parent > to get clk->parent->rate without first checking that clk->parent > was valid. This doesn't work if the clock is (A) a root clock > and (B) can change rate. Such is the case with a VCO clock > like the ICST which consequently crash like this without > this patch: > > Unable to handle kernel NULL pointer dereference at virtual address 0000001c > pgd = c0004000 > [0000001c] *pgd=00000000 > Internal error: Oops: 5 [#1] PREEMPT ARM > Modules linked in: > CPU: 0 Not tainted (3.5.0-rc3-00003-g8156866-dirty #193) > PC is at clk_change_rate+0x34/0xd8 > LR is at clk_change_rate+0x18/0xd8 > > Cc: stable@kernel.org > Cc: Mike Turquette > Cc: Ulf Hansson > Signed-off-by: Linus Walleij Hi Linus, This has been fixed in Pawell's patch, "clk: Check parent for NULL in clk_change_rate". Thanks, Mike > --- > drivers/clk/clk.c | 22 +++++++++++++++------- > 1 file changed, 15 insertions(+), 7 deletions(-) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index 687b00d..032d79c 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -854,14 +854,22 @@ static void clk_change_rate(struct clk *clk) > > old_rate = clk->rate; > > - if (clk->ops->set_rate) > - clk->ops->set_rate(clk->hw, clk->new_rate, clk->parent->rate); > + if (clk->ops->set_rate) { > + if (clk->parent) > + clk->ops->set_rate(clk->hw, clk->new_rate, > + clk->parent->rate); > + else > + clk->ops->set_rate(clk->hw, clk->new_rate, 0); > + } > > - if (clk->ops->recalc_rate) > - clk->rate = clk->ops->recalc_rate(clk->hw, > - clk->parent->rate); > - else > - clk->rate = clk->parent->rate; > + if (clk->ops->recalc_rate) { > + if (clk->parent) > + clk->rate = clk->ops->recalc_rate(clk->hw, > + clk->parent->rate); > + else > + clk->rate = clk->ops->recalc_rate(clk->hw, 0); > + } else > + clk->rate = clk->parent ? clk->parent->rate : 0; > > if (clk->notifier_count && old_rate != clk->rate) > __clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate); > -- > 1.7.10.4 >