On Thu, Nov 17, 2016 at 09:25:58AM -0500, Vince Weaver wrote: > On Thu, 17 Nov 2016, Josh Poimboeuf wrote: > > > On Thu, Nov 17, 2016 at 10:48:27AM +0100, Dmitry Vyukov wrote: > > > Just in case, there is currently a known KASAN false positive related > > > to longjmp's on GPFs. When a syscall hits GPF stack is unwound to > > > kernel entry point, this leaves a bunch of stray poisoned redzones on > > > the thread stack. They later cause false stack-out-of-bounds reports. > > > > > > But this does not seem to be the case here. Kernel is not tainted. And > > > shadow at the bottom of the reports looks sane. > > > > > > But if that's the case somehow, we will need to add > > > kasan_unpoison_remaining_stack() call before a longjmp like we did for > > > jprobe_return(): > > > https://groups.google.com/d/msg/kasan-dev/Hzox58yZ4MU/TOdFoWMuBQAJ > > > > I'm pretty sure this isn't a KASAN false positive. The unwinder does > > actually seem to be accessing a bad area of the stack, in the middle of > > a function's stack frame. > > I'm having trouble reproducing it on a few other machines I have fuzzing. > So there might be some kernel option contributing, I need to compare > .configs. > > Also the machine that easily triggers the problem I'm compiling with > gcc-5.4 where the machines I can't are using gcc-4.9.
I believe KASAN only works with gcc 5 and later, so that would explain why you aren't seeing it with gcc 4.9. -- Josh
