4.19-stable review patch. If anyone has any objections, please let me know.
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From: Logan Gunthorpe logang@deltatee.com
commit d2fd6e81912a665993b24dcdc1c1384a42a54f7e upstream.
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 After init, once the memory is freed, it is no longer valid to reference this pointer.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 c5eb1190074c ("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: aaca43fda742 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/pci/pci.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -6113,7 +6113,8 @@ 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);