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Tue, 29 Jun 2021 09:40:47 -0700 (PDT) MIME-Version: 1.0 References: <20210629161738.936790-1-glider@google.com> In-Reply-To: <20210629161738.936790-1-glider@google.com> From: Marco Elver Date: Tue, 29 Jun 2021 18:40:34 +0200 Message-ID: Subject: Re: [PATCH v2] kfence: skip DMA allocations 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 Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=qVLx61de; spf=pass (imf07.hostedemail.com: domain of elver@google.com designates 209.85.161.53 as permitted sender) smtp.mailfrom=elver@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 00997100008B X-Stat-Signature: 34b8auu61mfdwponby31kte9arunpd93 X-HE-Tag: 1624984847-741347 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 Tue, 29 Jun 2021 at 18:17, Alexander Potapenko wrote: > Allocation requests with __GFP_DMA/__GFP_DMA32 or > SLAB_CACHE_DMA/SLAB_CACHE_DMA32 cannot be fulfilled by KFENCE, because > they must reside in low memory, whereas KFENCE memory pool is located in > high memory. > > Skip such allocations to avoid crashes where DMAable memory is expected. > > Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") > 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 Thanks! > --- > > v2: > - added parentheses around the GFP clause, as requested by Marco > --- > mm/kfence/core.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mm/kfence/core.c b/mm/kfence/core.c > index 4d21ac44d5d35..f7ce3d876bc9e 100644 > --- a/mm/kfence/core.c > +++ b/mm/kfence/core.c > @@ -760,6 +760,14 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) > if (size > PAGE_SIZE) > return NULL; > > + /* > + * Skip DMA allocations. These must reside in the low memory, which we > + * cannot guarantee. > + */ > + if ((flags & (__GFP_DMA | __GFP_DMA32)) || > + (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32))) > + return NULL; > + > return kfence_guarded_alloc(s, size, flags); > } > > -- > 2.32.0.93.g670b81a890-goog >