Messages in this thread | | | Date | Mon, 28 Nov 2005 21:18:07 -0800 | From | Andrew Morton <> | Subject | Re: Fix crash when ptrace poking hugepage areas |
| |
David Gibson <david@gibson.dropbear.id.au> wrote: > > Bill, does this look like the correct fix for the problem to you? If > so, please apply Andrew. > > set_page_dirty() will not cope with being handed a page * which is > part of a compound page, but not the master page in that compound > page. This case can occur via access_process_vm() if you attempt to > write to another process's hugepage memory area using ptrace() > (causing an oops or hang). > > This patch fixes the bug by first resolving the page * to the compound > page's master page.
We already have to handle this situation for direct-io read()s into hugepages. bio_set_pages_dirty() does
if (page && !PageCompound(page)) set_page_dirty_lock(page);
It's such a rare case that it's probably best to continue to do this in the caller rather than in the callee. That's access_process_vm().
Unless there's a reason why we actually want the compound page to be marked dirty? If there is, then direct-io has a problem. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |