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[209.85.220.65]) by mx.google.com with SMTPS id p25sor1065412lfo.24.2019.06.07.13.08.08 for (Google Transport Security); Fri, 07 Jun 2019 13:08:08 -0700 (PDT) Received-SPF: pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=CI1ZG2by; spf=pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jrdr.linux@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=QDK3Ccwx6XT9W6QHiKSRwInuQJSgvhMen0AzjEbYCA8=; b=CI1ZG2byPK/1Kx8LZGxmpQVJbJPwAqQiJocZJTlvpGxmCbijp6s/MCkHKaIeulCqHm jkzBrAdWPEJYL7EChVEhSiSL7fH/uls6StJKdkrQ5+Q01AJSmPLrW82w/L+Hn1S73z+Q eyuKALMZREPHrLDajs0j38+UZFCBbs1bFRfrvM40LOT8ZeGSwORrXT3ZIw6l6e+DYtyO WHj3L2BKr8MObeNnmJF4CZwwqvoF+GvIu23HNTC/PhyX1ZAprAr1cMW2llBY8qa9UfbT n0rS9y7xpuoSaMNzM0KoPozltJ5AIo5wBfdosSEzNtv1l1F1knPWA4PyuP18dJYg4v87 a46w== X-Google-Smtp-Source: APXvYqwqkSPR8EIsmRv7XptKwGZtNlG6WGTa+Aw0Rgt8bmKe6Kk78did3YSh+DNFgKoB7girGDdcu1ECBFa9wEIQIxM= X-Received: by 2002:ac2:4ac5:: with SMTP id m5mr4305451lfp.95.1559938088611; Fri, 07 Jun 2019 13:08:08 -0700 (PDT) MIME-Version: 1.0 References: <20190523153436.19102-1-jgg@ziepe.ca> <20190523153436.19102-11-jgg@ziepe.ca> In-Reply-To: <20190523153436.19102-11-jgg@ziepe.ca> From: Souptick Joarder Date: Sat, 8 Jun 2019 01:43:12 +0530 Message-ID: Subject: Re: [RFC PATCH 10/11] mm/hmm: Poison hmm_range during unregister To: Jason Gunthorpe Cc: linux-rdma@vger.kernel.org, Linux-MM , Jerome Glisse , Ralph Campbell , John Hubbard , Jason Gunthorpe Content-Type: text/plain; charset="UTF-8" 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, May 23, 2019 at 9:05 PM 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 Acked-by: Souptick Joarder > --- > mm/hmm.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/mm/hmm.c b/mm/hmm.c > index 6c3b7398672c29..02752d3ef2ed92 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -936,8 +936,7 @@ EXPORT_SYMBOL(hmm_range_register); > */ > void hmm_range_unregister(struct hmm_range *range) > { > - /* Sanity check this really should not happen. */ > - if (range->hmm == NULL || range->end <= range->start) > + if (WARN_ON(range->end <= range->start)) > return; Does it make any sense to sanity check for range == NULL as well ? > > mutex_lock(&range->hmm->lock); > @@ -945,9 +944,13 @@ void hmm_range_unregister(struct hmm_range *range) > mutex_unlock(&range->hmm->lock); > > /* Drop reference taken by hmm_range_register() */ > - range->valid = false; > hmm_put(range->hmm); > - range->hmm = NULL; > + > + /* The range is now invalid, leave it poisoned. */ > + range->valid = false; > + range->start = ULONG_MAX; > + range->end = 0; > + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm)); > } > EXPORT_SYMBOL(hmm_range_unregister); > > -- > 2.21.0 >