Messages in this thread | | | Date | Mon, 14 Mar 2016 19:56:19 +0300 | Subject | Re: [PATCH v7 5/7] mm, kasan: Stackdepot implementation. Enable stackdepot for SLAB | From | Andrey Ryabinin <> |
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2016-03-14 13:43 GMT+03:00 Alexander Potapenko <glider@google.com>:
> + > + rec = this_cpu_ptr(&depot_recursion); > + /* Don't store the stack if we've been called recursively. */ > + if (unlikely(*rec)) > + goto fast_exit; > + *rec = true;
This just can't work. As long as preemption enabled, task could migrate on another cpu anytime. You could use per-task flag, although it's possible to miss some in-irq stacktraces:
depot_save_stack() if (current->stackdeport_recursion) goto fast_exit; current->stackdepot_recursion++ <IRQ> .... depot_save_stack() if (current->stackdeport_recursion) goto fast_exit;
> + if (unlikely(!smp_load_acquire(&next_slab_inited))) { > + /* Zero out zone modifiers, as we don't have specific zone > + * requirements. Keep the flags related to allocation in atomic > + * contexts and I/O. > + */ > + alloc_flags &= ~GFP_ZONEMASK; > + alloc_flags &= (GFP_ATOMIC | GFP_KERNEL); > + /* When possible, allocate using vmalloc() to reduce physical > + * address space fragmentation. vmalloc() doesn't work if > + * kmalloc caches haven't been initialized or if it's being > + * called from an interrupt handler. > + */ > + if (kmalloc_caches[KMALLOC_SHIFT_HIGH] && !in_interrupt()) {
This is clearly a wrong way to check whether is slab available or not. Besides you need to check vmalloc() for availability, not slab. Given that STAC_ALLOC_ORDER is 2 now, I think it should be fine to use alloc_pages() all the time. Or fix condition, up to you.
> + prealloc = __vmalloc( > + STACK_ALLOC_SIZE, alloc_flags, PAGE_KERNEL); > + } else { > + page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER); > + if (page) > + prealloc = page_address(page); > + } > + } > +
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