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* [PATCH v4 1/2] kfence: move the size check to the beginning of __kfence_alloc()
@ 2021-06-30 15:02 Alexander Potapenko
  2021-06-30 15:02 ` [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations Alexander Potapenko
  0 siblings, 1 reply; 5+ messages in thread
From: Alexander Potapenko @ 2021-06-30 15:02 UTC (permalink / raw)
  To: akpm
  Cc: dvyukov, elver, linux-kernel, linux-mm, stable, gregkh,
	jrdr.linux, Alexander Potapenko

Check the allocation size before toggling kfence_allocation_gate.
This way allocations that can't be served by KFENCE will not result in
waiting for another CONFIG_KFENCE_SAMPLE_INTERVAL without allocating
anything.

Suggested-by: Marco Elver <elver@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org # 5.12+
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Marco Elver <elver@google.com>
---
 mm/kfence/core.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 4d21ac44d5d35..33bb20d91bf6a 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -733,6 +733,13 @@ void kfence_shutdown_cache(struct kmem_cache *s)
 
 void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
 {
+	/*
+	 * Perform size check before switching kfence_allocation_gate, so that
+	 * we don't disable KFENCE without making an allocation.
+	 */
+	if (size > PAGE_SIZE)
+		return NULL;
+
 	/*
 	 * allocation_gate only needs to become non-zero, so it doesn't make
 	 * sense to continue writing to it and pay the associated contention
@@ -757,9 +764,6 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
 	if (!READ_ONCE(kfence_enabled))
 		return NULL;
 
-	if (size > PAGE_SIZE)
-		return NULL;
-
 	return kfence_guarded_alloc(s, size, flags);
 }
 
-- 
2.32.0.93.g670b81a890-goog


^ permalink raw reply	[flat|nested] 5+ messages in thread

* [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations
  2021-06-30 15:02 [PATCH v4 1/2] kfence: move the size check to the beginning of __kfence_alloc() Alexander Potapenko
@ 2021-06-30 15:02 ` Alexander Potapenko
  2021-07-05 14:05   ` Marco Elver
  2021-07-05 18:38   ` Souptick Joarder
  0 siblings, 2 replies; 5+ messages in thread
From: Alexander Potapenko @ 2021-06-30 15:02 UTC (permalink / raw)
  To: akpm
  Cc: dvyukov, elver, linux-kernel, linux-mm, stable, gregkh,
	jrdr.linux, Alexander Potapenko

Allocation requests outside ZONE_NORMAL (MOVABLE, HIGHMEM or DMA) cannot
be fulfilled by KFENCE, because KFENCE memory pool is located in a
zone different from the requested one.

Because callers of kmem_cache_alloc() may actually rely on the
allocation to reside in the requested zone (e.g. memory allocations done
with __GFP_DMA must be DMAable), skip all allocations done with
GFP_ZONEMASK and/or respective SLAB flags (SLAB_CACHE_DMA and
SLAB_CACHE_DMA32).

Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: stable@vger.kernel.org # 5.12+
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Marco Elver <elver@google.com>

---

v2:
 - added parentheses around the GFP clause, as requested by Marco
v3:
 - ignore GFP_ZONEMASK, which also covers __GFP_HIGHMEM and __GFP_MOVABLE
 - move the flag check at the beginning of the function, as requested by
   Souptick Joarder
v4:
 - minor fixes to description and comment formatting
---
 mm/kfence/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 33bb20d91bf6a..1cbdb62e6d0fb 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -740,6 +740,15 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
 	if (size > PAGE_SIZE)
 		return NULL;
 
+	/*
+	 * Skip allocations from non-default zones, including DMA. We cannot
+	 * guarantee that pages in the KFENCE pool will have the requested
+	 * properties (e.g. reside in DMAable memory).
+	 */
+	if ((flags & GFP_ZONEMASK) ||
+	    (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32)))
+		return NULL;
+
 	/*
 	 * allocation_gate only needs to become non-zero, so it doesn't make
 	 * sense to continue writing to it and pay the associated contention
-- 
2.32.0.93.g670b81a890-goog


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations
  2021-06-30 15:02 ` [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations Alexander Potapenko
@ 2021-07-05 14:05   ` Marco Elver
  2021-07-13 16:19     ` Marco Elver
  2021-07-05 18:38   ` Souptick Joarder
  1 sibling, 1 reply; 5+ messages in thread
From: Marco Elver @ 2021-07-05 14:05 UTC (permalink / raw)
  To: akpm
  Cc: dvyukov, linux-kernel, linux-mm, stable, gregkh, jrdr.linux,
	Alexander Potapenko

Andrew,

This series is ready to be picked up.

If possible, kindly consider including it in an upcoming batch of
mainline fixes.

Thank you!


On Wed, 30 Jun 2021 at 17:02, Alexander Potapenko <glider@google.com> wrote:
> Allocation requests outside ZONE_NORMAL (MOVABLE, HIGHMEM or DMA) cannot
> be fulfilled by KFENCE, because KFENCE memory pool is located in a
> zone different from the requested one.
>
> Because callers of kmem_cache_alloc() may actually rely on the
> allocation to reside in the requested zone (e.g. memory allocations done
> with __GFP_DMA must be DMAable), skip all allocations done with
> GFP_ZONEMASK and/or respective SLAB flags (SLAB_CACHE_DMA and
> SLAB_CACHE_DMA32).
>
> Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Souptick Joarder <jrdr.linux@gmail.com>
> Cc: stable@vger.kernel.org # 5.12+
> Signed-off-by: Alexander Potapenko <glider@google.com>
> Reviewed-by: Marco Elver <elver@google.com>
>
> ---
>
> v2:
>  - added parentheses around the GFP clause, as requested by Marco
> v3:
>  - ignore GFP_ZONEMASK, which also covers __GFP_HIGHMEM and __GFP_MOVABLE
>  - move the flag check at the beginning of the function, as requested by
>    Souptick Joarder
> v4:
>  - minor fixes to description and comment formatting
> ---
>  mm/kfence/core.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index 33bb20d91bf6a..1cbdb62e6d0fb 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -740,6 +740,15 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
>         if (size > PAGE_SIZE)
>                 return NULL;
>
> +       /*
> +        * Skip allocations from non-default zones, including DMA. We cannot
> +        * guarantee that pages in the KFENCE pool will have the requested
> +        * properties (e.g. reside in DMAable memory).
> +        */
> +       if ((flags & GFP_ZONEMASK) ||
> +           (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32)))
> +               return NULL;
> +
>         /*
>          * allocation_gate only needs to become non-zero, so it doesn't make
>          * sense to continue writing to it and pay the associated contention
> --
> 2.32.0.93.g670b81a890-goog
>

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations
  2021-06-30 15:02 ` [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations Alexander Potapenko
  2021-07-05 14:05   ` Marco Elver
@ 2021-07-05 18:38   ` Souptick Joarder
  1 sibling, 0 replies; 5+ messages in thread
From: Souptick Joarder @ 2021-07-05 18:38 UTC (permalink / raw)
  To: Alexander Potapenko
  Cc: Andrew Morton, Dmitry Vyukov, Marco Elver, linux-kernel,
	Linux-MM, stable, Greg KH

On Wed, Jun 30, 2021 at 8:32 PM Alexander Potapenko <glider@google.com> wrote:
>
> Allocation requests outside ZONE_NORMAL (MOVABLE, HIGHMEM or DMA) cannot
> be fulfilled by KFENCE, because KFENCE memory pool is located in a
> zone different from the requested one.
>
> Because callers of kmem_cache_alloc() may actually rely on the
> allocation to reside in the requested zone (e.g. memory allocations done
> with __GFP_DMA must be DMAable), skip all allocations done with
> GFP_ZONEMASK and/or respective SLAB flags (SLAB_CACHE_DMA and
> SLAB_CACHE_DMA32).
>
> Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Souptick Joarder <jrdr.linux@gmail.com>
> Cc: stable@vger.kernel.org # 5.12+
> Signed-off-by: Alexander Potapenko <glider@google.com>
> Reviewed-by: Marco Elver <elver@google.com>
>
> ---
>
> v2:
>  - added parentheses around the GFP clause, as requested by Marco
> v3:
>  - ignore GFP_ZONEMASK, which also covers __GFP_HIGHMEM and __GFP_MOVABLE
>  - move the flag check at the beginning of the function, as requested by
>    Souptick Joarder

Acked-by: Souptick Joarder <jrdr.linux@gmail.com>

> v4:
>  - minor fixes to description and comment formatting
> ---
>  mm/kfence/core.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index 33bb20d91bf6a..1cbdb62e6d0fb 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -740,6 +740,15 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
>         if (size > PAGE_SIZE)
>                 return NULL;
>
> +       /*
> +        * Skip allocations from non-default zones, including DMA. We cannot
> +        * guarantee that pages in the KFENCE pool will have the requested
> +        * properties (e.g. reside in DMAable memory).
> +        */
> +       if ((flags & GFP_ZONEMASK) ||
> +           (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32)))
> +               return NULL;
> +
>         /*
>          * allocation_gate only needs to become non-zero, so it doesn't make
>          * sense to continue writing to it and pay the associated contention
> --
> 2.32.0.93.g670b81a890-goog
>

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations
  2021-07-05 14:05   ` Marco Elver
@ 2021-07-13 16:19     ` Marco Elver
  0 siblings, 0 replies; 5+ messages in thread
From: Marco Elver @ 2021-07-13 16:19 UTC (permalink / raw)
  To: akpm
  Cc: dvyukov, linux-kernel, linux-mm, stable, gregkh, jrdr.linux,
	Alexander Potapenko

On Mon, 5 Jul 2021 at 16:05, Marco Elver <elver@google.com> wrote:
> Andrew,
>
> This series is ready to be picked up.
>
> If possible, kindly consider including it in an upcoming batch of
> mainline fixes.
>
> Thank you!

It'd be good to get this sorted -- please take another look.

Many thanks,
-- Marco

> On Wed, 30 Jun 2021 at 17:02, Alexander Potapenko <glider@google.com> wrote:
> > Allocation requests outside ZONE_NORMAL (MOVABLE, HIGHMEM or DMA) cannot
> > be fulfilled by KFENCE, because KFENCE memory pool is located in a
> > zone different from the requested one.
> >
> > Because callers of kmem_cache_alloc() may actually rely on the
> > allocation to reside in the requested zone (e.g. memory allocations done
> > with __GFP_DMA must be DMAable), skip all allocations done with
> > GFP_ZONEMASK and/or respective SLAB flags (SLAB_CACHE_DMA and
> > SLAB_CACHE_DMA32).
> >
> > Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Marco Elver <elver@google.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: Souptick Joarder <jrdr.linux@gmail.com>
> > Cc: stable@vger.kernel.org # 5.12+
> > Signed-off-by: Alexander Potapenko <glider@google.com>
> > Reviewed-by: Marco Elver <elver@google.com>
> >
> > ---
> >
> > v2:
> >  - added parentheses around the GFP clause, as requested by Marco
> > v3:
> >  - ignore GFP_ZONEMASK, which also covers __GFP_HIGHMEM and __GFP_MOVABLE
> >  - move the flag check at the beginning of the function, as requested by
> >    Souptick Joarder
> > v4:
> >  - minor fixes to description and comment formatting
> > ---
> >  mm/kfence/core.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> > index 33bb20d91bf6a..1cbdb62e6d0fb 100644
> > --- a/mm/kfence/core.c
> > +++ b/mm/kfence/core.c
> > @@ -740,6 +740,15 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
> >         if (size > PAGE_SIZE)
> >                 return NULL;
> >
> > +       /*
> > +        * Skip allocations from non-default zones, including DMA. We cannot
> > +        * guarantee that pages in the KFENCE pool will have the requested
> > +        * properties (e.g. reside in DMAable memory).
> > +        */
> > +       if ((flags & GFP_ZONEMASK) ||
> > +           (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32)))
> > +               return NULL;
> > +
> >         /*
> >          * allocation_gate only needs to become non-zero, so it doesn't make
> >          * sense to continue writing to it and pay the associated contention
> > --
> > 2.32.0.93.g670b81a890-goog
> >

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2021-07-13 16:19 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2021-06-30 15:02 [PATCH v4 1/2] kfence: move the size check to the beginning of __kfence_alloc() Alexander Potapenko
2021-06-30 15:02 ` [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations Alexander Potapenko
2021-07-05 14:05   ` Marco Elver
2021-07-13 16:19     ` Marco Elver
2021-07-05 18:38   ` Souptick Joarder

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