On 05/02, Kirill A. Shutemov wrote: > > On Mon, May 02, 2016 at 04:15:38PM +0200, Oleg Nesterov wrote: > > > > > > - I don't see any check page_count() around __replace_page() in uprobes, > > > so it can easily replace pinned page. > > > > Why it should? even if it races with get_user_pages_fast()... this doesn't > > differ from the case when an application writes to MAP_PRIVATE non-anonymous > > region, no? > > < I know nothing about uprobes or ptrace in general > > > I think the difference is that the write is initiated by the process > itself, but IIUC __replace_page() can be initiated by other process, so > it's out of control of the application. Yes. Just like gdb can insert a breakpoint into the read-only executable vma. > So we have pages pinned by a driver and the driver expects the pinned > pages to be mapped into userspace, then __replace_page() kicks in and put > different page there -- driver's expectation is broken. Yes... but I don't understand the problem space. I mean, I do not know why this driver should expect this, how it can be broken, etc. I do not even understand why "initiated by other process" can make any difference... Unless this driver somehow controls all threads which could have this page mapped. Oleg. -- 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>