On Wed, 2019-09-04 at 16:13 +0200, Vlastimil Babka wrote: > On 9/4/19 4:06 PM, Walter Wu wrote: > > On Wed, 2019-09-04 at 14:49 +0200, Vlastimil Babka wrote: > >> On 9/4/19 8:51 AM, Walter Wu wrote: > >> > This patch is KASAN report adds the alloc/free stacks for page allocator > >> > in order to help programmer to see memory corruption caused by page. > >> > > >> > By default, KASAN doesn't record alloc/free stack for page allocator. > >> > It is difficult to fix up page use-after-free issue. > >> > > >> > This feature depends on page owner to record the last stack of pages. > >> > It is very helpful for solving the page use-after-free or out-of-bound. > >> > > >> > KASAN report will show the last stack of page, it may be: > >> > a) If page is in-use state, then it prints alloc stack. > >> > It is useful to fix up page out-of-bound issue. > >> > >> I expect this will conflict both in syntax and semantics with my series [1] that > >> adds the freeing stack to page_owner when used together with debug_pagealloc, > >> and it's now in mmotm. Glad others see the need as well :) Perhaps you could > >> review the series, see if it fulfils your usecase (AFAICS the series should be a > >> superset, by storing both stacks at once), and perhaps either make KASAN enable > >> debug_pagealloc, or turn KASAN into an alternative enabler of the functionality > >> there? > >> > >> Thanks, Vlastimil > >> > >> [1] https://lore.kernel.org/linux-mm/20190820131828.22684-1-vbabka@xxxxxxx/t/#u > >> > > Thanks your information. > > We focus on the smartphone, so it doesn't enable > > CONFIG_TRANSPARENT_HUGEPAGE, Is it invalid for our usecase? > > The THP fix is not required for the rest of the series, it was even merged to > mainline separately. > > > And It looks like something is different, because we only need last > > stack of page, so it can decrease memory overhead. > > That would save you depot_stack_handle_t (which is u32) per page. I guess that's > nothing compared to KASAN overhead? > If we can use less memory, we can achieve what we want. Why not? Thanks. Walter
