On Wed, Aug 08, 2012 at 03:50:46PM -0700, David Miller wrote: > From: Mel Gorman <mgorman@xxxxxxx> > Date: Tue, 7 Aug 2012 09:55:55 +0100 > > > Commit [c48a11c7: netvm: propagate page->pfmemalloc to skb] is responsible > > for the following bug triggered by a xen network driver > ... > > The problem is that the xenfront driver is passing a NULL page to > > __skb_fill_page_desc() which was unexpected. This patch checks that > > there is a page before dereferencing. > > > > Reported-and-Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> > > Signed-off-by: Mel Gorman <mgorman@xxxxxxx> > > That call to __skb_fill_page_desc() in xen-netfront.c looks completely bogus. > It's the only driver passing NULL here. It looks to be passing a valid page pointer (at least by looking at the code) so I am not sure how it got turned in a NULL. But let me double-check by instrumenting the driver.. > > That whole song and dance figuring out what to do with the head > fragment page, depending upon whether the length is greater than the > RX_COPY_THRESHOLD, is completely unnecessary. > > Just use something like a call to __pskb_pull_tail(skb, len) and all > that other crap around that area can simply be deleted. It looks like an overkill - it does a lot more than just allocate an SKB and a page. Deleting of extra code would be nice - however I am not going to be able to do that for the next two weeks sadly - as my plate if full of debugging some other stuff. Lets see if Ian has some time. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>