On Tue, 14 Jan 2020 15:31:36 +0530 "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> wrote: > This is a repost of patch series from Peter with the arch specific changes except ppc64 dropped. > ppc64 changes are added here because we are redoing the patch series on top of ppc64 changes. This makes it > easy to backport these changes. Only the first 3 patches need to be backported to stable. But none of these patches had a cc:stable in the changelog? > The thing is, on anything SMP, freeing page directories should observe the > exact same order as normal page freeing: > > 1) unhook page/directory > 2) TLB invalidate > 3) free page/directory > > Without this, any concurrent page-table walk could end up with a Use-after-Free. > This is esp. trivial for anything that has software page-table walkers > (HAVE_FAST_GUP / software TLB fill) or the hardware caches partial page-walks > (ie. caches page directories). > > Even on UP this might give issues since mmu_gather is preemptible these days. > An interrupt or preempted task accessing user pages might stumble into the free > page if the hardware caches page directories. > > This patch series fixup ppc64 and add generic MMU_GATHER changes to support the conversion of other architectures. > I haven't added patches w.r.t other architecture because they are yet to be acked.
