Re: [PATCH 5.0 25/89] RDMA/ucontext: Fix regression with disassociate

[Michal Kubecek]

On Fri, May 03, 2019 at 01:47:16PM +0200, Michal Kubecek wrote:
> On Tue, Apr 30, 2019 at 01:38:16PM +0200, Greg Kroah-Hartman wrote:
> > From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
> > 
> > commit 67f269b37f9b4d52c5e7f97acea26c0852e9b8a1 upstream.
> > 
> > When this code was consolidated the intention was that the VMA would
> > become backed by anonymous zero pages after the zap_vma_pte - however this
> > very subtly relied on setting the vm_ops = NULL and clearing the VM_SHARED
> > bits to transform the VMA into an anonymous VMA. Since the vm_ops was
> > removed this broke.
> > 
> > Now userspace gets a SIGBUS if it touches the vma after disassociation.
> > 
> > Instead of converting the VMA to anonymous provide a fault handler that
> > puts a zero'd page into the VMA when user-space touches it after
> > disassociation.
> > 
> > Cc: stable@xxxxxxxxxxxxxxx
> > Suggested-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> > Fixes: 5f9794dc94f5 ("RDMA/ucontext: Add a core API for mmaping driver IO memory")
> > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
> > Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
> > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > 
> > ---
> 
> This commit breaks build on s390 and mips, please pick also commit
> 6a5c5d26c4c6 ("rdma: fix build errors on s390 and MIPS due to bad
> ZERO_PAGE use").

Oops, it's already there as 71/89, I managed to overlook it. Sorry for
the noise.

Michal Kubecek