Messages in this thread | | | Date | Fri, 07 Nov 2014 12:21:02 +0000 | From | Zoltan Kiss <> | Subject | Re: [Xen-devel] BUG in xennet_make_frags with paged skb data |
| |
On 07/11/14 12:15, Stefan Bader wrote: > On 07.11.2014 12:22, Eric Dumazet wrote: >> On Fri, 2014-11-07 at 09:25 +0000, Zoltan Kiss wrote: >> >> Please do not top post. >> >>> Hi, >>> >>> AFAIK in this scenario your skb frag is wrong. The page pointer should >>> point to the original compound page (not a member of it), and offset >>> should be set accordingly. >>> For example, if your compound page is 16K (4 page), then the page >>> pointer should point to the first page, and if the data starts at the >>> 3rd page, then offset should be >8K >> >> This is not accurate. >> >> This BUG_ON() is wrong. >> >> It should instead be : >> >> BUG_ON(len + offset > PAGE_SIZE<<compound_order(compound_head(page))); > > would that not have to be > > BUG_ON((page-compound_head(page)*PAGE_SIZE)+offset+len > > PAGE_SIZE<<compound_order(compound_head(page)));
There should be a parentheses around "page-compound_head(page)". > > since offset is adjusted to start from the tail page in that case. >> >> splice() code can generate such cases. >> >> > >
| |