[PATCH] cciss: Make cciss_seq_show handle holes in the h->drv[] array.

[PATCH] cciss: Make cciss_seq_show handle holes in the h->drv[] array.

[Stephen M. Cameron]

From: Stephen M. Cameron <scameron@beardog.cce.hp.com>

cciss: Make cciss_seq_show handle holes in the h->drv[] array.
It is possible (and expected) for there to be holes in the h->drv[]
array, that is, some elements may be NULL pointers.  cciss_seq_show
needs to be made aware of this possibility to avoid an Oops.

To reproduce the Oops which this fixes:

1) Create two "arrays" in the Array Configuratino Utility and
   several logical drives on each array.
2) cat /proc/driver/cciss/cciss* in an infinite loop
3) delete some of the logical drives in the first "array."

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
---
 drivers/block/cciss.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 873e594..9291614 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -337,6 +337,9 @@ static int cciss_seq_show(struct seq_file *seq, void *v)
 	if (*pos > h->highest_lun)
 		return 0;
 
+	if (drv == NULL) /* it's possible for h->drv[] to have holes. */
+		return 0;
+
 	if (drv->heads == 0)
 		return 0;
 

Re: [PATCH] cciss: Make cciss_seq_show handle holes in the h->drv[] array.

[Jens Axboe]

On Thu, Feb 04 2010, Stephen M. Cameron wrote:
> From: Stephen M. Cameron <scameron@beardog.cce.hp.com>
> 
> cciss: Make cciss_seq_show handle holes in the h->drv[] array.
> It is possible (and expected) for there to be holes in the h->drv[]
> array, that is, some elements may be NULL pointers.  cciss_seq_show
> needs to be made aware of this possibility to avoid an Oops.
> 
> To reproduce the Oops which this fixes:
> 
> 1) Create two "arrays" in the Array Configuratino Utility and
>    several logical drives on each array.
> 2) cat /proc/driver/cciss/cciss* in an infinite loop
> 3) delete some of the logical drives in the first "array."
> 
> Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>

Thanks Stephen, applied for 2.6.33. BTW, you want to put that stable cc
into the patch itself as well, then it'll get picked up automatically
when Linus merges it.

-- 
Jens Axboe