From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 625DBC4332F for ; Sun, 11 Dec 2022 11:19:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230166AbiLKLTR (ORCPT ); Sun, 11 Dec 2022 06:19:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230057AbiLKLTP (ORCPT ); Sun, 11 Dec 2022 06:19:15 -0500 Received: from vps0.lunn.ch (vps0.lunn.ch [156.67.10.101]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC11655B3 for ; Sun, 11 Dec 2022 03:19:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:From:Sender:Reply-To:Subject: Date:Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Content-Disposition:In-Reply-To:References; bh=1/0PqUsOmRXu/00wK7b4mz01EtG5IQc3H88g2/V7PHg=; b=DYdAD2kgel8YV+Y6+KyH5MEWYV yfEeeMsW96JmtOMDNDZEAzumlJt+ydROS1U+vMtfceYdn/veMY2Dz+LIw9zFssh55YgBXX+yQtgv8 Cgv4jHw/grBYXbHSmX/zqH+6i7+6RqcGK5TN08gUIqvnBLadGTOd3t3IAUGcxIYBPO9U=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1p4KM5-0050ph-Jo; Sun, 11 Dec 2022 12:18:49 +0100 Date: Sun, 11 Dec 2022 12:18:49 +0100 From: Andrew Lunn To: Piergiorgio Beruto Cc: Giuseppe Cavallaro , Alexandre Torgue , Jose Abreu , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Maxime Coquelin , Richard Cochran , Julien Beraud , netdev@vger.kernel.org Subject: Re: [PATCH v2 net 1/1] stmmac: fix potential division by 0 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, Dec 10, 2022 at 11:37:22PM +0100, Piergiorgio Beruto wrote: > When the MAC is connected to a 10 Mb/s PHY and the PTP clock is derived > from the MAC reference clock (default), the clk_ptp_rate becomes too > small and the calculated sub second increment becomes 0 when computed by > the stmmac_config_sub_second_increment() function within > stmmac_init_tstamp_counter(). > > Therefore, the subsequent div_u64 in stmmac_init_tstamp_counter() > operation triggers a divide by 0 exception as shown below. > > [ 95.062067] socfpga-dwmac ff700000.ethernet eth0: Register MEM_TYPE_PAGE_POOL RxQ-0 > [ 95.076440] socfpga-dwmac ff700000.ethernet eth0: PHY [stmmac-0:08] driver [NCN26000] (irq=49) > [ 95.095964] dwmac1000: Master AXI performs any burst length > [ 95.101588] socfpga-dwmac ff700000.ethernet eth0: No Safety Features support found > [ 95.109428] Division by zero in kernel. > [ 95.113447] CPU: 0 PID: 239 Comm: ifconfig Not tainted 6.1.0-rc7-centurion3-1.0.3.0-01574-gb624218205b7-dirty #77 > [ 95.123686] Hardware name: Altera SOCFPGA > [ 95.127695] unwind_backtrace from show_stack+0x10/0x14 > [ 95.132938] show_stack from dump_stack_lvl+0x40/0x4c > [ 95.137992] dump_stack_lvl from Ldiv0+0x8/0x10 > [ 95.142527] Ldiv0 from __aeabi_uidivmod+0x8/0x18 > [ 95.147232] __aeabi_uidivmod from div_u64_rem+0x1c/0x40 > [ 95.152552] div_u64_rem from stmmac_init_tstamp_counter+0xd0/0x164 > [ 95.158826] stmmac_init_tstamp_counter from stmmac_hw_setup+0x430/0xf00 > [ 95.165533] stmmac_hw_setup from __stmmac_open+0x214/0x2d4 > [ 95.171117] __stmmac_open from stmmac_open+0x30/0x44 > [ 95.176182] stmmac_open from __dev_open+0x11c/0x134 > [ 95.181172] __dev_open from __dev_change_flags+0x168/0x17c > [ 95.186750] __dev_change_flags from dev_change_flags+0x14/0x50 > [ 95.192662] dev_change_flags from devinet_ioctl+0x2b4/0x604 > [ 95.198321] devinet_ioctl from inet_ioctl+0x1ec/0x214 > [ 95.203462] inet_ioctl from sock_ioctl+0x14c/0x3c4 > [ 95.208354] sock_ioctl from vfs_ioctl+0x20/0x38 > [ 95.212984] vfs_ioctl from sys_ioctl+0x250/0x844 > [ 95.217691] sys_ioctl from ret_fast_syscall+0x0/0x4c > [ 95.222743] Exception stack(0xd0ee1fa8 to 0xd0ee1ff0) > [ 95.227790] 1fa0: 00574c4f be9aeca4 00000003 00008914 be9aeca4 be9aec50 > [ 95.235945] 1fc0: 00574c4f be9aeca4 0059f078 00000036 be9aee8c be9aef7a 00000015 00000000 > [ 95.244096] 1fe0: 005a01f0 be9aec38 004d7484 b6e67d74 > > Signed-off-by: Piergiorgio Beruto > Fixes: 91a2559c1dc5 ("net: stmmac: Fix sub-second increment") Reviewed-by: Andrew Lunn Andrew