On Mon, 15 Sep 2014, Joonsoo Kim wrote: > On Thu, Sep 11, 2014 at 10:32:52PM -0400, Mikulas Patocka wrote: > > > > > > On Mon, 8 Sep 2014, Christoph Lameter wrote: > > > > > On Mon, 8 Sep 2014, Mikulas Patocka wrote: > > > > > > > I don't know what you mean. If someone allocates 10000 objects with sizes > > > > from 1 to 10000, you can't have 10000 slab caches - you can't have a slab > > > > cache for each used size. Also - you can't create a slab cache in > > > > interrupt context. > > > > > > Oh you can create them up front on bootup. And I think only the small > > > sizes matter. Allocations >=8K are pushed to the page allocator anyways. > > > > Only for SLUB. For SLAB, large allocations are still use SLAB caches up to > > 4M. But anyway - having 8K preallocated slab caches is too much. > > > > If you want to integrate this patch into the slab/slub subsystem, a better > > solution would be to store the exact size requested with kmalloc along the > > slab/slub object itself (before the preceding redzone). But it would > > result in duplicating the work - you'd have to repeat the logic in this > > patch three times - once for slab, once for slub and once for > > kmalloc_large/kmalloc_large_node. > > > > I don't know if it would be better than this patch. > > Hello, > > Out of bound write could be detected by kernel address asanitizer(KASan). > See following link. > > https://lkml.org/lkml/2014/9/10/441 > > Although this patch also looks good to me, I think that KASan is > better than this, because it could detect out of bound write and > has more features for debugging. > > Thanks. Surely, KAsan detects more bugs. But it has also high overhead. The overhead of kmalloc guard is very low. The kmalloc guard already helped to find one previously unknown bug: http://lkml.iu.edu/hypermail/linux/kernel/1409.1/02325.html Mikulas -- 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>