PCI: Fix __initdata issue with "pci=disable_acs_redir" parameter

lsgunth · bjorn-helgaas · commit d2fd6e81912a · 2019-01-17T08:46:34.000-06:00
The disable_acs_redir parameter stores a pointer to the string passed to pci_setup(). However, the string passed to PCI setup is actually a temporary copy allocated in static __initdata memory. After init, once the memory is freed, it is no longer valid to reference this pointer. This bug was noticed in v5.0-rc1 after a change in commit c5eb119 ("PCI / PM: Allow runtime PM without callback functions") caused pci_disable_acs_redir() to be called during shutdown which manifested as an unable to handle kernel paging request at: RIP: 0010:pci_enable_acs+0x3f/0x1e0 Call Trace: pci_restore_state.part.44+0x159/0x3c0 pci_restore_standard_config+0x33/0x40 pci_pm_runtime_resume+0x2b/0xd0 ? pci_restore_standard_config+0x40/0x40 __rpm_callback+0xbc/0x1b0 rpm_callback+0x1f/0x70 ? pci_restore_standard_config+0x40/0x40 rpm_resume+0x4f9/0x710 ? pci_conf1_read+0xb6/0xf0 ? pci_conf1_write+0xb2/0xe0 __pm_runtime_resume+0x47/0x70 pci_device_shutdown+0x1e/0x60 device_shutdown+0x14a/0x1f0 kernel_restart+0xe/0x50 __do_sys_reboot+0x1ee/0x210 ? __fput+0x144/0x1d0 do_writev+0x5e/0xf0 ? do_writev+0x5e/0xf0 do_syscall_64+0x48/0xf0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 It was also likely possible to trigger this bug when hotplugging PCI devices. To fix this, instead of storing a pointer, we use kstrdup() to copy the disable_acs_redir_param to its own buffer which will never be freed. Fixes: aaca43f ("PCI: Add "pci=disable_acs_redir=" parameter for peer-to-peer support") Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> Signed-off-by: Logan Gunthorpe <logang@deltatee.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
@@ -6195,7 +6195,8 @@ static int __init pci_setup(char *str)
 			} else if (!strncmp(str, "pcie_scan_all", 13)) {
 				pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
 			} else if (!strncmp(str, "disable_acs_redir=", 18)) {
-				disable_acs_redir_param = str + 18;
+				disable_acs_redir_param =
+					kstrdup(str + 18, GFP_KERNEL);
 			} else {
 				printk(KERN_ERR "PCI: Unknown option `%s'\n",
 						str);
