On Mon, Sep 06, 2021, Paolo Bonzini wrote: > On 20/08/21 20:51, Mathieu Desnoyers wrote: > > > Ah, or is it the case that rseq_cs is non-NULL if and only if userspace is in an > > > rseq critical section, and because syscalls in critical sections are illegal, by > > > definition clearing rseq_cs is a nop unless userspace is misbehaving. > > Not quite, as I described above. But we want it to stay set so the CONFIG_DEBUG_RSEQ > > code executed when returning from ioctl to userspace will be able to validate that > > it is not nested within a rseq critical section. > > > > > If that's true, what about explicitly checking that at NOTIFY_RESUME? Or is it > > > not worth the extra code to detect an error that will likely be caught anyways? > > The error will indeed already be caught on return from ioctl to userspace, so I > > don't see any added value in duplicating this check. > > Sean, can you send a v2 (even for this patch only would be okay)? Made it all the way to v3 while you were out :-) https://lkml.kernel.org/r/20210901203030.1292304-1-seanjc@xxxxxxxxxx
