From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 8D80E1400B7 for ; Thu, 10 Apr 2014 19:16:00 +1000 (EST) Message-ID: <1397116463.3671.181.camel@pasglop> Subject: Re: [PATCH] Fix 3bc95598 'powerpc/PCI: Use list_for_each_entry() for bus traversal' From: Benjamin Herrenschmidt To: Mike Qiu Date: Thu, 10 Apr 2014 17:54:23 +1000 In-Reply-To: <1397112695-3945-1-git-send-email-qiudayu@linux.vnet.ibm.com> References: <1397112695-3945-1-git-send-email-qiudayu@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: bhelgaas@google.com, paulus@samba.org, wangyijing@huawei.com, linuxppc-dev@lists.ozlabs.org, anton@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2014-04-10 at 02:51 -0400, Mike Qiu wrote: > Unable to handle kernel paging request for data at address 0x00000000 > Faulting instruction address: 0xc000000000041d78 > Oops: Kernel access of bad area, sig: 11 [#1] > ... > NIP [c000000000041d78] .sys_pciconfig_iobase+0x68/0x1f0 > LR [c000000000041e0c] .sys_pciconfig_iobase+0xfc/0x1f0 > Call Trace: > [c0000003b4787db0] [c000000000041e0c] .sys_pciconfig_iobase+0xfc/0x1f0 (unreliable) > [c0000003b4787e30] [c000000000009ed8] syscall_exit+0x0/0x98 > > This bug was introduced by commit 3bc955987fb377f3c95bc29deb498e96819b8451 > The root cause was the 'bus' has been set to null while try to access > bus->next. Good catch. Out of curiosity, what is using that syscall nowadays ? It's been long buggy in all sort of ways and is pretty much deprecated... Cheers, Ben. > Signed-off-by: Mike Qiu > --- > arch/powerpc/kernel/pci_64.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c > index 2a47790..7b6c1ae 100644 > --- a/arch/powerpc/kernel/pci_64.c > +++ b/arch/powerpc/kernel/pci_64.c > @@ -209,6 +209,7 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus, > { > struct pci_controller* hose; > struct pci_bus *bus = NULL; > + struct pci_bus *tmp_bus = NULL; > struct device_node *hose_node; > > /* Argh ! Please forgive me for that hack, but that's the > @@ -229,10 +230,12 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus, > * used on pre-domains setup. We return the first match > */ > > - list_for_each_entry(bus, &pci_root_buses, node) { > - if (in_bus >= bus->number && in_bus <= bus->busn_res.end) > + list_for_each_entry(tmp_bus, &pci_root_buses, node) { > + if (in_bus >= tmp_bus->number && > + in_bus <= tmp_bus->busn_res.end) { > + bus = tmp_bus; > break; > - bus = NULL; > + } > } > if (bus == NULL || bus->dev.of_node == NULL) > return -ENODEV;