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Wed, 30 Jun 2021 07:05:12 -0700 (PDT) MIME-Version: 1.0 References: <20210630135313.1072577-1-glider@google.com> In-Reply-To: <20210630135313.1072577-1-glider@google.com> From: Marco Elver Date: Wed, 30 Jun 2021 16:05:00 +0200 Message-ID: Subject: Re: [PATCH v3 1/2] kfence: move the size check to the beginning of __kfence_alloc() To: Alexander Potapenko Cc: akpm@linux-foundation.org, dvyukov@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, gregkh@linuxfoundation.org, jrdr.linux@gmail.com Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=oayVw5cj; spf=pass (imf16.hostedemail.com: domain of elver@google.com designates 209.85.167.177 as permitted sender) smtp.mailfrom=elver@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: CB0FBF00009D X-Stat-Signature: nnwi5jzmdjw1b8oz8bay7ft4am44i9cw X-HE-Tag: 1625061913-651705 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 30 Jun 2021 at 15:53, Alexander Potapenko 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 > Cc: Andrew Morton > Cc: Dmitry Vyukov > Cc: Marco Elver > Cc: Greg Kroah-Hartman > Cc: stable@vger.kernel.org # 5.12+ > Signed-off-by: Alexander Potapenko Reviewed-by: Marco Elver > --- > 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 >