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Wed, 30 Jun 2021 08:02:38 -0700 (PDT) Date: Wed, 30 Jun 2021 17:02:33 +0200 Message-Id: <20210630150234.1109496-1-glider@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.32.0.93.g670b81a890-goog Subject: [PATCH v4 1/2] kfence: move the size check to the beginning of __kfence_alloc() From: Alexander Potapenko To: akpm@linux-foundation.org Cc: dvyukov@google.com, elver@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, gregkh@linuxfoundation.org, jrdr.linux@gmail.com, Alexander Potapenko Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=UedDNaHa; spf=pass (imf24.hostedemail.com: domain of 3jofcYAYKCB09EB67K9HH9E7.5HFEBGNQ-FFDO35D.HK9@flex--glider.bounces.google.com designates 209.85.221.74 as permitted sender) smtp.mailfrom=3jofcYAYKCB09EB67K9HH9E7.5HFEBGNQ-FFDO35D.HK9@flex--glider.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: zx6m3589ips9hdsrzjffza77sb1qtcm6 X-Rspamd-Queue-Id: BC8DAB0000B6 X-Rspamd-Server: rspam06 X-HE-Tag: 1625065359-981541 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: 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); }