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Date: Wed, 19 Jun 2019 10:41:12 -0600 From: Khalid Aziz <khalid.aziz@...cle.com> To: Andrey Konovalov <andreyknvl@...gle.com>, linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org, linux-media@...r.kernel.org, kvm@...r.kernel.org, linux-kselftest@...r.kernel.org Cc: Catalin Marinas <catalin.marinas@....com>, Vincenzo Frascino <vincenzo.frascino@....com>, Will Deacon <will.deacon@....com>, Mark Rutland <mark.rutland@....com>, Andrew Morton <akpm@...ux-foundation.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Kees Cook <keescook@...omium.org>, Yishai Hadas <yishaih@...lanox.com>, Felix Kuehling <Felix.Kuehling@....com>, Alexander Deucher <Alexander.Deucher@....com>, Christian Koenig <Christian.Koenig@....com>, Mauro Carvalho Chehab <mchehab@...nel.org>, Jens Wiklander <jens.wiklander@...aro.org>, Alex Williamson <alex.williamson@...hat.com>, Leon Romanovsky <leon@...nel.org>, Luc Van Oostenryck <luc.vanoostenryck@...il.com>, Dave Martin <Dave.Martin@....com>, enh <enh@...gle.com>, Jason Gunthorpe <jgg@...pe.ca>, Christoph Hellwig <hch@...radead.org>, Dmitry Vyukov <dvyukov@...gle.com>, Kostya Serebryany <kcc@...gle.com>, Evgeniy Stepanov <eugenis@...gle.com>, Lee Smith <Lee.Smith@....com>, Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>, Jacob Bramley <Jacob.Bramley@....com>, Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>, Robin Murphy <robin.murphy@....com>, Kevin Brodsky <kevin.brodsky@....com>, Szabolcs Nagy <Szabolcs.Nagy@....com> Subject: Re: [PATCH v17 05/15] mm, arm64: untag user pointers in mm/gup.c On 6/12/19 5:43 AM, Andrey Konovalov wrote: > This patch is a part of a series that extends arm64 kernel ABI to allow to > pass tagged user pointers (with the top byte set to something else other > than 0x00) as syscall arguments. > > mm/gup.c provides a kernel interface that accepts user addresses and > manipulates user pages directly (for example get_user_pages, that is used > by the futex syscall). Since a user can provided tagged addresses, we need > to handle this case. > > Add untagging to gup.c functions that use user addresses for vma lookups. > > Reviewed-by: Kees Cook <keescook@...omium.org> > Reviewed-by: Catalin Marinas <catalin.marinas@....com> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com> > --- Reviewed-by: Khalid Aziz <khalid.aziz@...cle.com> > mm/gup.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index ddde097cf9e4..c37df3d455a2 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -802,6 +802,8 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > if (!nr_pages) > return 0; > > + start = untagged_addr(start); > + > VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); > > /* > @@ -964,6 +966,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, > struct vm_area_struct *vma; > vm_fault_t ret, major = 0; > > + address = untagged_addr(address); > + > if (unlocked) > fault_flags |= FAULT_FLAG_ALLOW_RETRY; > >
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