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Mon, 05 Jul 2021 11:39:00 -0700 (PDT) MIME-Version: 1.0 References: <20210630150234.1109496-1-glider@google.com> <20210630150234.1109496-2-glider@google.com> In-Reply-To: <20210630150234.1109496-2-glider@google.com> From: Souptick Joarder Date: Tue, 6 Jul 2021 00:08:48 +0530 Message-ID: Subject: Re: [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations To: Alexander Potapenko Cc: Andrew Morton , Dmitry Vyukov , Marco Elver , linux-kernel@vger.kernel.org, Linux-MM , stable@vger.kernel.org, Greg KH Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 46C59D007F1A X-Stat-Signature: 6frbqhx8rgyarybaz5r5wwwoho9fsbbd Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=LUzCOtv0; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf21.hostedemail.com: domain of jrdrlinux@gmail.com designates 209.85.221.179 as permitted sender) smtp.mailfrom=jrdrlinux@gmail.com X-HE-Tag: 1625510341-240490 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, Jun 30, 2021 at 8:32 PM Alexander Potapenko 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 > Cc: Dmitry Vyukov > Cc: Marco Elver > Cc: Greg Kroah-Hartman > Cc: Souptick Joarder > Cc: stable@vger.kernel.org # 5.12+ > Signed-off-by: Alexander Potapenko > Reviewed-by: Marco Elver > > --- > > 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 > 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 >