On 1/14/20 4:20 PM, Peter Zijlstra wrote:
On Tue, Jan 14, 2020 at 03:31:36PM +0530, Aneesh Kumar K.V 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.
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.
Obviously looks good to me; will you route this through the Power tree
since you're in a hurry to see this fixed?
Michael,
Can you take this via your tree?
-aneesh
