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[134.134.136.20]) by mx.google.com with ESMTPS id b6si3294288pgq.465.2019.06.07.16.00.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 07 Jun 2019 16:00:24 -0700 (PDT) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 134.134.136.20 as permitted sender) client-ip=134.134.136.20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 134.134.136.20 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Jun 2019 16:00:24 -0700 X-ExtLoop1: 1 Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by orsmga002.jf.intel.com with ESMTP; 07 Jun 2019 16:00:23 -0700 Date: Fri, 7 Jun 2019 16:01:37 -0700 From: Ira Weiny To: Jason Gunthorpe Cc: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com, linux-rdma@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Jason Gunthorpe Subject: Re: [PATCH v2 hmm 09/11] mm/hmm: Poison hmm_range during unregister Message-ID: <20190607230136.GH14559@iweiny-DESK2.sc.intel.com> References: <20190606184438.31646-1-jgg@ziepe.ca> <20190606184438.31646-10-jgg@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190606184438.31646-10-jgg@ziepe.ca> User-Agent: Mutt/1.11.1 (2018-12-01) 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 Thu, Jun 06, 2019 at 03:44:36PM -0300, Jason Gunthorpe wrote: > From: Jason Gunthorpe > > Trying to misuse a range outside its lifetime is a kernel bug. Use WARN_ON > and poison bytes to detect this condition. > > Signed-off-by: Jason Gunthorpe > Reviewed-by: Jérôme Glisse > --- > v2 > - Keep range start/end valid after unregistration (Jerome) > --- > mm/hmm.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/hmm.c b/mm/hmm.c > index 6802de7080d172..c2fecb3ecb11e1 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -937,7 +937,7 @@ void hmm_range_unregister(struct hmm_range *range) > struct hmm *hmm = range->hmm; > > /* Sanity check this really should not happen. */ > - if (hmm == NULL || range->end <= range->start) > + if (WARN_ON(range->end <= range->start)) > return; > > mutex_lock(&hmm->lock); > @@ -948,7 +948,10 @@ void hmm_range_unregister(struct hmm_range *range) > range->valid = false; > mmput(hmm->mm); > hmm_put(hmm); > - range->hmm = NULL; > + > + /* The range is now invalid, leave it poisoned. */ > + range->valid = false; No need to set valid false again as you just did this 5 lines above. Reviewed-by: Ira Weiny > + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm)); > } > EXPORT_SYMBOL(hmm_range_unregister); > > -- > 2.21.0 >