Subject: Re: [PATCH] eeh: Fixing a bug when pci structure is null

From: Wolfram Sang <[email-masked]>
Date: Tue, 2 Feb 2010 19:05:03 +0100

On Tue, Feb 02, 2010 at 03:46:28PM -0200, Breno Leitao wrote:
>  During a EEH recover, the pci_dev structure can be null, mainly if an
>  eeh event is detected during cpi config operation. In this case, the
>  pci_dev will not be known (and will be null) and the kernel will crash
>  with the following message:
>  
>  Unable to handle kernel paging request for data at address 0x000000a0
>  Faulting instruction address: 0xc00000000006b8b4
>  Oops: Kernel access of bad area, sig: 11 [#1]
>  
>  NIP [c00000000006b8b4] .eeh_event_handler+0x10c/0x1a0
>  LR [c00000000006b8a8] .eeh_event_handler+0x100/0x1a0
>  Call Trace:
>  [c0000003a80dff00] [c00000000006b8a8] .eeh_event_handler+0x100/0x1a0
>  [c0000003a80dff90] [c000000000031f1c] .kernel_thread+0x54/0x70
>  
>  The bug occurs because pci_name() tries to access a null pointer.
>  This patch just guarantee that pci_name() is not called on Null pointers.
>  
>  Signed-off-by: Breno Leitao <[email-masked]>
>  Signed-off-by: Linas Vepstas <[email-masked]>
>  ---
>   arch/powerpc/include/asm/ppc-pci.h          |    7 +++++++
>   arch/powerpc/platforms/pseries/eeh.c        |    4 ++--
>   arch/powerpc/platforms/pseries/eeh_driver.c |    4 ++--
>   arch/powerpc/platforms/pseries/eeh_event.c  |    2 +-
>   4 files changed, 12 insertions(+), 5 deletions(-)
>  
>  diff --git a/arch/powerpc/include/asm/ppc-pci.h b/arch/powerpc/include/asm/ppc-pci.h
>  index 2828f9d..724dbe2 100644
>  --- a/arch/powerpc/include/asm/ppc-pci.h
>  +++ b/arch/powerpc/include/asm/ppc-pci.h
>  @@ -137,6 +137,13 @@ struct device_node * find_device_pe(struct device_node *dn);
>   void eeh_sysfs_add_device(struct pci_dev *pdev);
>   void eeh_sysfs_remove_device(struct pci_dev *pdev);
>  
>  +static inline const char *eeh_pci_name(struct pci_dev *pdev) 
>  +{ 
>  +	if (NULL==pdev) 
>  +		return "<null>"; 
>  +	return pci_name(pdev); 

What about:

	return pdev ? pci_name(pdev) : "<null>";

>  +} 
>  +
>   #endif /* CONFIG_EEH */
>  
>   #else /* CONFIG_PCI */
>  diff --git a/arch/powerpc/platforms/pseries/eeh.c b/arch/powerpc/platforms/pseries/eeh.c
>  index ccd8dd0..f9360fe 100644
>  --- a/arch/powerpc/platforms/pseries/eeh.c
>  +++ b/arch/powerpc/platforms/pseries/eeh.c
>  @@ -491,7 +491,7 @@ int eeh_dn_check_failure(struct device_node *dn, struct pci_dev *dev)
>   	    pdn->eeh_mode & EEH_MODE_NOCHECK) {
>   		ignored_check++;
>   		pr_debug("EEH: Ignored check (%x) for %s %s\n",
>  -			 pdn->eeh_mode, pci_name (dev), dn->full_name);
>  +			 pdn->eeh_mode, eeh_pci_name (dev), dn->full_name);

No space after function name, please.

>   		return 0;
>   	}
>  
>  @@ -515,7 +515,7 @@ int eeh_dn_check_failure(struct device_node *dn, struct pci_dev *dev)
>   			printk (KERN_ERR "EEH: %d reads ignored for recovering device at "
>   				"location=%s driver=%s pci addr=%s\n",
>   				pdn->eeh_check_count, location,
>  -				dev->driver->name, pci_name(dev));
>  +				dev->driver->name, eeh_pci_name(dev));

ditto

>   			printk (KERN_ERR "EEH: Might be infinite loop in %s driver\n",
>   				dev->driver->name);
>   			dump_stack();
>  diff --git a/arch/powerpc/platforms/pseries/eeh_driver.c b/arch/powerpc/platforms/pseries/eeh_driver.c
>  index ef8e454..8f948a0 100644
>  --- a/arch/powerpc/platforms/pseries/eeh_driver.c
>  +++ b/arch/powerpc/platforms/pseries/eeh_driver.c
>  @@ -337,7 +337,7 @@ struct pci_dn * handle_eeh_events (struct eeh_event *event)
>   		location = location ? location : "unknown";
>   		printk(KERN_ERR "EEH: Error: Cannot find partition endpoint "
>   		                "for location=%s pci addr=%s\n",
>  -		        location, pci_name(event->dev));
>  +		        location, eeh_pci_name(event->dev));
>   		return NULL;
>   	}
>  
>  @@ -368,7 +368,7 @@ struct pci_dn * handle_eeh_events (struct eeh_event *event)
>   		pci_str = pci_name (frozen_pdn->pcidev);
>   		drv_str = pcid_name (frozen_pdn->pcidev);
>   	} else {
>  -		pci_str = pci_name (event->dev);
>  +		pci_str = eeh_pci_name (event->dev);

ditto

>   		drv_str = pcid_name (event->dev);
>   	}
>   	
>  diff --git a/arch/powerpc/platforms/pseries/eeh_event.c b/arch/powerpc/platforms/pseries/eeh_event.c
>  index ddb80f5..ec5df8f 100644
>  --- a/arch/powerpc/platforms/pseries/eeh_event.c
>  +++ b/arch/powerpc/platforms/pseries/eeh_event.c
>  @@ -80,7 +80,7 @@ static int eeh_event_handler(void * dummy)
>   	eeh_mark_slot(event->dn, EEH_MODE_RECOVERING);
>  
>   	printk(KERN_INFO "EEH: Detected PCI bus error on device %s\n",
>  -	       pci_name(event->dev));
>  +	       eeh_pci_name(event->dev));
>  
>   	pdn = handle_eeh_events(event);
> _______________________________________________
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> [email-masked]
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Pengutronix e.K.                           | Wolfram Sang                |
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