On Thu, Aug 18, 2016 at 4:36 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: > On Wed, Aug 17, 2016 at 05:29:31PM -0400, Rob Clark wrote: >> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c >> index 6cd4af4..4502e4b 100644 >> --- a/drivers/gpu/drm/msm/msm_gem.c >> +++ b/drivers/gpu/drm/msm/msm_gem.c >> @@ -201,6 +201,13 @@ int msm_gem_fault(struct vm_area_struct *vma, >> struct vm_fault *vmf) >> pgoff_t pgoff; >> int ret; >> >> + /* I think this should only happen if userspace tries to pass a >> + * mmap'd but unfaulted gem bo vaddr into submit ioctl, triggering >> + * a page fault while struct_mutex is already held >> + */ >> + if (mutex_is_locked_by(&dev->struct_mutex, current)) >> + return VM_FAULT_SIGBUS; > > This is an ok (well still horrible) heuristics for the shrinker, but for > correctness it kinda doesn't cut it. What you need to do instead is drop > all the locks, copy relocations into a temp memory area and then proceed > in the msm command submission path above. > > Also reentrant mutexes are evil ;-) Please note that this is not a reentrant mutex in the fault path, it bails with VM_FAULT_SIGBUG! There is never a legit reason to use a gem bo for the bos (or cmds) table in the ioctl, so while this may not be pretty, I believe it is an acceptable solution. BR, -R -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
