| Message ID | 20210630135313.1072577-1-glider@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3,1/2] kfence: move the size check to the beginning of __kfence_alloc() | expand |
On Wed, 30 Jun 2021 at 15:53, Alexander Potapenko <glider@google.com> wrote: > > 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 >
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); }
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> --- mm/kfence/core.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)