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From: Neil Brown <neilb@suse.de>
To: David Chinner <dgc@sgi.com>
Date: Tue, 4 Dec 2007 11:14:12 +1100
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Subject: Re: Regression - 2.6.24-rc3 - umem nvram card driver oops
In-Reply-To: message from David Chinner on Tuesday December 4
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On Tuesday December 4, dgc@sgi.com wrote:
> Neil,
> 
> I just upgraded an ia64 (Altix, 16k page size) test box to 2.6.24-rc3
> from 2.6.23 and I get it panicing on boot in the umem driver.

Cool - someone is using umem!  And even testing it.  Thanks!

A quick look shows a probable NULL deref.  Let me know if this fixes
it.  I'll read through the offending patch more carefully and make
sure there is nothing else wrong.

NeilBrown


Fix possible NULL dereference in umem.c

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./drivers/block/umem.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff .prev/drivers/block/umem.c ./drivers/block/umem.c
--- .prev/drivers/block/umem.c	2007-12-04 11:11:30.000000000 +1100
+++ ./drivers/block/umem.c	2007-12-04 11:11:42.000000000 +1100
@@ -484,7 +484,8 @@ static void process_page(unsigned long d
 		page->idx++;
 		if (page->idx >= bio->bi_vcnt) {
 			page->bio = bio->bi_next;
-			page->idx = page->bio->bi_idx;
+			if (page->bio)
+				page->idx = page->bio->bi_idx;
 		}
 
 		pci_unmap_page(card->dev, desc->data_dma_handle,