On 03/02/2012 04:57 PM, Linus Torvalds wrote: > On Fri, Mar 2, 2012 at 4:38 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote: >> >> My biggest concern is what happens when this happens to be at the end of >> mapped kernel memory and we overrun the page? > > Yes. It's very unlikely, and it never happens with the dentry data > itself (the name is always aligned for those). > > But it *can* happen if: > > - the page contains the filename we copied from user space > > - the page is the last page mapped > > - the filename is PATH_MAX in size (or very close) > > - the last component is sufficiently unaligned > > but I was thinking we'd just make sure not to free the last page, and > just solve it that way. > > I was playing around with other ideas (take the page fault and fix it > up), but those are all really complicated when the notion of "don't > use the last page" is so much simpler. > Note that does mean we need a guard page after each and every discontiguous RAM range, not just the last one. Raising that issue since we have had serious bugs in that area in the past. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
