On Fri, Aug 30, 2019 at 08:30:00AM -0700, Linus Torvalds wrote: > On Fri, Aug 30, 2019 at 7:08 AM Russell King - ARM Linux admin > <[email protected]> wrote: > > > > which means that when probe_kernel_address() returns -EFAULT, the > > destination is left uninitialised. In the case of > > task_rcu_dereference(), this means that "siginfo" can be used without > > having been initialised, resulting in this function returning an > > indeterminant result (based on the value of an uninitialised variable > > on the stack.) > > Do you actually see that behavior?
No, it was an observation of the code. > Because the foillowing lines: > > smp_rmb(); > if (unlikely(task != READ_ONCE(*ptask))) > goto retry; > > are what is supposed to protect it - yes, it could have faulted, but > only if 'task' isn't valid any more, and we just re-checked it. Ah, ok. Might be worth some comments - I find the comments in that function particularly unhelpful (even after Oleg mentions this is case 2.) -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
