On Mon, Jul 04, 2016 at 02:07:30PM +0900, Sergey Senozhatsky wrote: > Hello, > > On (07/04/16 13:57), Joonsoo Kim wrote: > > On Sun, Jul 03, 2016 at 01:16:56AM +0900, Sergey Senozhatsky wrote: > > > Introduce PAGE_OWNER_TRACK_FREE config option to extend page owner with > > > free_pages() tracking functionality. This adds to the dump_page_owner() > > > output an additional backtrace, that tells us what path has freed the > > > page. > > > > Hmm... Do you have other ideas to use this feature? Following example is > > just to detect use-after-free and we have other good tools for it > > (KASAN or DEBUG_PAGEALLOC) so I'm not sure whether it's useful or not. > > there is no kasan for ARM32, for example (apart from the fact that > it's really hard to use kasan sometimes due to its cpu cycles and > memory requirements). Hmm... for debugging purpose, KASAN provides many more things so IMO it's better to implement/support KASAN in ARM32 rather than expand PAGE_OWNER for free. > > educate me, will DEBUG_PAGEALLOC tell us what path has triggered the > extra put_page()? hm... does ARM32 provide ARCH_SUPPORTS_DEBUG_PAGEALLOC? Hmm... Now, I notice that PAGE_OWNER_TRACK_FREE will detect double-free rather than use-after-free. DEBUG_PAGEALLOC doesn't catch double-free but it can be implemented easily. In this case, we can show call path for second free. AFAIK, ARM32 doesn't support ARCH_SUPPORTS_DEBUG_PAGEALLOC. Thanks. -- 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>