Messages in this thread | | | Subject | Re: [patch 7/7] PCI/AER: Fix the broken interrupt injection | From | Kuppuswamy Sathyanarayanan <> | Date | Fri, 6 Mar 2020 11:29:30 -0800 |
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On 3/6/20 10:32 AM, Kuppuswamy Sathyanarayanan wrote: > > On 3/6/20 5:03 AM, Thomas Gleixner wrote: >> The AER error injection mechanism just blindly abuses >> generic_handle_irq() >> which is really not meant for consumption by random drivers. The >> include of >> linux/irq.h should have been a red flag in the first place. Driver code, >> unless implementing interrupt chips or low level hypervisor >> functionality >> has absolutely no business with that. >> >> Invoking generic_handle_irq() from non interrupt handling context can >> have >> nasty side effects at least on x86 due to the hardware trainwreck which >> makes interrupt affinity changes a fragile beast. Sathyanarayanan >> triggered >> a NULL pointer dereference in the low level APIC code that way. While >> the >> particular pointer could be checked this would only paper over the issue >> because there are other ways to trigger warnings or silently corrupt >> state. >> >> Invoke the new irq_inject_interrupt() mechanism, which has the necessary >> sanity checks in place and injects the interrupt via the irq_retrigger() >> mechanism, which is at least halfways safe vs. the fragile x86 affinity >> change mechanics. >> >> It's safe on x86 as it does not corrupt state, but it still can cause a >> premature completion of an interrupt affinity change causing the >> interrupt >> line to become stale. Very unlikely, but possible. >> >> For regular operations this is a non issue as AER error injection is >> meant >> for debugging and testing and not for usage on production systems. >> People >> using this should better know what they are doing. > It looks good to me. > > Reviewed-by: Kuppuswamy Sathyanarayanan > <sathyanarayanan.kuppuswamy@linux.intel.com> > Tested-by: Kuppuswamy Sathyanarayanan > <sathyanarayanan.kuppuswamy@linux.intel.com> >> >> Fixes: 390e2db82480 ("PCI/AER: Abstract AER interrupt handling") This patch is merged in v4.20 kernel. So this fix could be a candidate for stable fix. >> Reported-by: sathyanarayanan.kuppuswamy@linux.intel.com >> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> >> --- >> drivers/pci/pcie/Kconfig | 1 + >> drivers/pci/pcie/aer_inject.c | 6 ++---- >> 2 files changed, 3 insertions(+), 4 deletions(-) >> >> --- a/drivers/pci/pcie/Kconfig >> +++ b/drivers/pci/pcie/Kconfig >> @@ -34,6 +34,7 @@ config PCIEAER >> config PCIEAER_INJECT >> tristate "PCI Express error injection support" >> depends on PCIEAER >> + select GENERIC_IRQ_INJECTION >> help >> This enables PCI Express Root Port Advanced Error Reporting >> (AER) software error injector. >> --- a/drivers/pci/pcie/aer_inject.c >> +++ b/drivers/pci/pcie/aer_inject.c >> @@ -16,7 +16,7 @@ >> #include <linux/module.h> >> #include <linux/init.h> >> -#include <linux/irq.h> >> +#include <linux/interrupt.h> >> #include <linux/miscdevice.h> >> #include <linux/pci.h> >> #include <linux/slab.h> >> @@ -468,9 +468,7 @@ static int aer_inject(struct aer_error_i >> } >> pci_info(edev->port, "Injecting errors %08x/%08x into >> device %s\n", >> einj->cor_status, einj->uncor_status, pci_name(dev)); >> - local_irq_disable(); >> - generic_handle_irq(edev->irq); >> - local_irq_enable(); >> + ret = irq_inject_interrupt(edev->irq); >> } else { >> pci_err(rpdev, "AER device not found\n"); >> ret = -ENODEV; >> -- Sathyanarayanan Kuppuswamy Linux kernel developer
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