Messages in this thread | | | Subject | Re: [PATCH] PCI: fix using __initdata memory after free in disable_acs_redir parameter | From | Jarkko Nikula <> | Date | Wed, 16 Jan 2019 11:37:46 +0200 |
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Hi
On 1/15/19 7:32 PM, Logan Gunthorpe wrote: > 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 the memory is freed, it is no longer valid to reference this pointer.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
So this doesn't happen if you revert c5eb1190074c?
I guess this is due dev->state_saved being true set by pci_pm_runtime_suspend() -> pci_save_state() after my patch and now pci_pm_runtime_resume() -> pci_restore_standard_config() -> pci_restore_state() reach the pci_enable_acs(). I think this is possible to trigger also before my patch if device has the runtime PM callback defined?
> 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. > I wasn't able to trigger this but I saw "PCI: Can't parse disable_acs_redir parameter: " followed by a few lines of junk during boot when I defined pci=disable_acs_redir=0000:00:xy.z which disappear after your patch.
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
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