From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754451AbcJETHY (ORCPT ); Wed, 5 Oct 2016 15:07:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34166 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752840AbcJETHT (ORCPT ); Wed, 5 Oct 2016 15:07:19 -0400 Date: Wed, 5 Oct 2016 21:07:16 +0200 From: Jiri Olsa To: "Theodore Ts'o" , "H. Peter Anvin" , Greg Price , lkml Subject: Re: [PATCH] random: Fix early crash in credit_entropy_bits Message-ID: <20161005190716.GA28329@krava> References: <1474470431-27532-1-git-send-email-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1474470431-27532-1-git-send-email-jolsa@kernel.org> User-Agent: Mutt/1.7.0 (2016-08-17) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 05 Oct 2016 19:07:19 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ping thanks, jirka On Wed, Sep 21, 2016 at 05:07:11PM +0200, Jiri Olsa wrote: > From: Jiri Olsa > > When printing out some early acpi messages I hit bug in > work queue code. The system_wq is not initialized at the > time acpi_early_init is called and causes irq storm that > makes credit_entropy_bits call schedule_work and crash: > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000102^M > IP: [] __queue_work+0x32/0x450^M > PGD 0 ^M > Oops: 0000 [#1] SMP^M > ... > Call Trace:^M > [ 286.521689] [] ? _raw_write_unlock_irqrestore+0x16/0x20^M > [] ? add_interrupt_randomness+0x1c2/0x200^M > [] queue_work_on+0x27/0x40^M > [] credit_entropy_bits+0x219/0x280^M > [] ? __mix_pool_bytes+0x36/0x90^M > [] add_interrupt_randomness+0x1c2/0x200^M > [] handle_irq_event_percpu+0x40/0x80^M > [] handle_irq_event+0x2c/0x50^M > [] handle_level_irq+0x83/0x100^M > [] handle_irq+0x73/0x120^M > [] ? _local_bh_enable+0x21/0x50^M > [] do_IRQ+0x4b/0xd0^M > [] common_interrupt+0x8c/0x8c^M > [ 286.521717] [] ? native_restore_fl+0x6/0x10^M > [] console_unlock+0x3ef/0x5d0^M > [] ? update_sample+0x6e/0xe0^M > [] vprintk_emit+0x2aa/0x520^M > [] vprintk_default+0x1f/0x30^M > [] printk+0x57/0x73^M > [] acpi_os_vprintf+0x3f/0x41^M > [] acpi_os_printf+0x52/0x6e^M > ... > [] acpi_load_tables+0x6c/0xf4^M > [] acpi_early_init+0x7a/0xf0^M > [] start_kernel+0x3be/0x472^M > > Preventing this by checking the system_wq has been initialized already. > > Signed-off-by: Jiri Olsa > --- > drivers/char/random.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/char/random.c b/drivers/char/random.c > index 3efb3bf0ab83..f4dec86c2e25 100644 > --- a/drivers/char/random.c > +++ b/drivers/char/random.c > @@ -725,7 +725,8 @@ retry: > /* If the input pool is getting full, send some > * entropy to the blocking pool until it is 75% full. > */ > - if (entropy_bits > random_write_wakeup_bits && > + if (keventd_up() && > + entropy_bits > random_write_wakeup_bits && > r->initialized && > r->entropy_total >= 2*random_read_wakeup_bits) { > struct entropy_store *other = &blocking_pool; > -- > 2.7.4 >