From mboxrd@z Thu Jan 1 00:00:00 1970 From: helgaas@kernel.org (Bjorn Helgaas) Date: Mon, 7 Mar 2016 16:33:11 -0600 Subject: [PATCH] Fix NULL ptr dereference in pci_bus_assign_domain_nr() on ARM In-Reply-To: References: Message-ID: <20160307223311.GB26149@localhost> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org [+cc Lorenzo] On Tue, Mar 01, 2016 at 07:07:18AM +0100, Krzysztof Ha?asa wrote: > Many ARM platforms use a wrapper: > /* > * Compatibility wrapper for older platforms that do not care about > * passing the parent device. > */ > static inline void pci_common_init(struct hw_pci *hw) > { > pci_common_init_dev(NULL, hw); > } > > which means that pci_bus_assign_domain_nr() can be called without > a parent. This patch fixes the NULL pointer dereference. > > Signed-off-by: Krzysztof Ha?asa > Cc: stable at vger.kernel.org I applied this to for-linus with changelog as below for v4.5, thanks! Wow, this is terrible. All ARM32 systems that use pci_common_init() crash at boot. That includes cns3xxx, dove, footbridge, iopl13xx, ip32x, iop33x, ixp4xx, ks8695, mv78xx0, orion5x, pxa, sa1100, etc. Apparently they've been crashing since v4.0, when 7c674700098c and 8c7d14746abc appeared. I can hardly believe nobody noticed until now. Actually, I did find one problem report: http://forum.doozan.com/read.php?2,17868,22070,quote=1 from last May, but apparently it got lost in a forum and never found its way upstream. I reworked the changelog because this problem will affect *any* arch that enables CONFIG_PCI_DOMAINS_GENERIC and supplies NULL "parent" pointers -- ia64, mips, mn10300, s390, x86, etc., would be affected if they enabled CONFIG_PCI_DOMAINS_GENERIC. I also added a "Fixes:" tag for 7c674700098c, since that's the commit that added the generic code we're fixing. Backports of 7c674700098c should also backport this change. Bjorn commit 71babd2a89fe Author: Krzysztof =?utf-8?Q?Ha=C5=82asa?= Date: Tue Mar 1 07:07:18 2016 +0100 PCI: Allow a NULL "parent" pointer in pci_bus_assign_domain_nr() pci_create_root_bus() passes a "parent" pointer to pci_bus_assign_domain_nr(). When CONFIG_PCI_DOMAINS_GENERIC is defined, pci_bus_assign_domain_nr() dereferences that pointer. Many callers of pci_create_root_bus() supply a NULL "parent" pointer, which leads to a NULL pointer dereference error. 7c674700098c ("PCI: Move domain assignment from arm64 to generic code") moved the "parent" dereference from arm64 to generic code. Only arm64 used that code (because only arm64 defined CONFIG_PCI_DOMAINS_GENERIC), and it always supplied a valid "parent" pointer. Other arches supplied NULL "parent" pointers but didn't defined CONFIG_PCI_DOMAINS_GENERIC, so they used a no-op version of pci_bus_assign_domain_nr(). 8c7d14746abc ("ARM/PCI: Move to generic PCI domains") defined CONFIG_PCI_DOMAINS_GENERIC on ARM, and many ARM platforms use pci_common_init(), which supplies a NULL "parent" pointer. These platforms (cns3xxx, dove, footbridge, iop13xx, etc.) crash with a NULL pointer dereference like this while probing PCI: Unable to handle kernel NULL pointer dereference at virtual address 000000a4 PC is at pci_bus_assign_domain_nr+0x10/0x84 LR is at pci_create_root_bus+0x48/0x2e4 Kernel panic - not syncing: Attempted to kill init! [bhelgaas: changelog, add "Reported:" and "Fixes:" tags] Reported: http://forum.doozan.com/read.php?2,17868,22070,quote=1 Fixes: 8c7d14746abc ("ARM/PCI: Move to generic PCI domains") Fixes: 7c674700098c ("PCI: Move domain assignment from arm64 to generic code") Signed-off-by: Krzysztof Ha?asa Signed-off-by: Bjorn Helgaas CC: stable at vger.kernel.org # v4.0+ diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 602eb42..f89db3a 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4772,8 +4772,10 @@ int pci_get_new_domain_nr(void) void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent) { static int use_dt_domains = -1; - int domain = of_get_pci_domain_nr(parent->of_node); + int domain = -1; + if (parent) + domain = of_get_pci_domain_nr(parent->of_node); /* * Check DT domain and use_dt_domains values. *