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memory is freed, it is no longer valid to reference this pointer.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 c5eb119007
("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: aaca43fda7 ("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>
d2fd6e8191