On Sun, Oct 30, 2016 at 8:44 AM, Jann Horn <j...@thejh.net> wrote: > free_pardevice() is called by parport_unregister_device() and already frees > pp->pdev->name, don't try to do it again. > > This bug causes kernel crashes. > > I found and verified this with KASAN and some added pr_emerg()s: > > [ 60.316568] pp_release: pp->pdev->name == ffff88039cb264c0 > [ 60.316692] free_pardevice: freeing par_dev->name at ffff88039cb264c0 > [ 60.316706] pp_release: kfree(ffff88039cb264c0) > [ 60.316714] ========================================================== > [ 60.316722] BUG: Double free or freeing an invalid pointer > [ 60.316731] Unexpected shadow byte: 0xFB > [ 60.316801] Object at ffff88039cb264c0, in cache kmalloc-32 size: 32 > [ 60.316813] Allocated: > [ 60.316824] PID = 1695 > [ 60.316869] Freed: > [ 60.316880] PID = 1695 > [ 60.316935] ========================================================== > > CCing Andy Lutomirski because I think this is what broke vmapped stacks > for me - after applying this patch, vmapped stacks worked for me. > Previously, I got oopses (and lockups) caused by area->pages[0] being > 0x400000000 in __vunmap(), with area->pages being allocated in the kmalloc > area.
That's an odd symptom. I assume that what's happening is that the pages array is being freed early by the extra kfree in here and then getting corrupted. --Andy
