On 07/10/2016 03:47 PM, Andy Lutomirski wrote: > Hi all- > > I found two nasty issues with virtually mapped stacks if KASAN is > enabled. The first issue is a crash: the first non-init stack is > allocated and accessed before KASAN initializes its zero shadow > AFAICT, which means that we switch to that stack and then blow up when > we start recursively faulting on failed accesses to the shadow. >
KASAN initialized quite early, before any non-init task exists. The crash happens because non-init task writes to write-protected zero shadow. Currently KASAN doesn't allocate shadow memory for vmalloc addresses, we just map single zero page and write protect it. > The second issue is that, even if we survive (we initialize the zero > shadow on time), KASAN will fail to protect hte stack. > > For now, I just disabled use of virtually mapped stacks if KASAN is > on. Do you have any easy ideas to fix it? > Allocate shadow memory which backs vmalloc/vmap allocations is the only way to fix this. I can do this, and post the patches soon enough. > Thanks, > Andy >