On Tue, Apr 05, 2016 at 03:36:57PM +0200, Lars Ellenberg wrote: > blk_check_plugged() will return a pointer > to an object linked on current->plug->cb_list. > > That list may "at any time" be implicitly cleared by > blk_flush_plug_list() > flush_plug_callbacks() > either as a result of blk_finish_plug(), > or implicitly by schedule() [and maybe other implicit mechanisms?] > > If there is no protection against an implicit unplug > between the call to blk_check_plug() and using its return value, > that implicit unplug may have already happened, > even before the plug is actually initialized or populated, > and we may be using a pointer to already free()d data. > > I suggest that both raid1 and raid10 can easily be fixed > by moving the call to blk_check_plugged() inside the spinlock. > > For md/raid5 and btrfs/raid56, > I'm unsure how (if) this needs to be fixed. I think you're right, digging in to see if there's something I missed. But as Neil said, it looks like we just got saved by preemption being off by default. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
