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[192.55.52.136]) by mx.google.com with ESMTPS id t74si3782171pgc.265.2019.05.30.14.46.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 May 2019 14:46:34 -0700 (PDT) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.136 as permitted sender) client-ip=192.55.52.136; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.136 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 May 2019 14:46:34 -0700 X-ExtLoop1: 1 Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by orsmga007.jf.intel.com with ESMTP; 30 May 2019 14:46:33 -0700 Date: Thu, 30 May 2019 14:47:26 -0700 From: Ira Weiny To: Pingfan Liu Cc: linux-mm@kvack.org, Andrew Morton , Mike Rapoport , Dan Williams , Matthew Wilcox , John Hubbard , "Aneesh Kumar K.V" , Keith Busch , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/gup: fix omission of check on FOLL_LONGTERM in get_user_pages_fast() Message-ID: <20190530214726.GA14000@iweiny-DESK2.sc.intel.com> References: <1559170444-3304-1-git-send-email-kernelfans@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1559170444-3304-1-git-send-email-kernelfans@gmail.com> 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, May 30, 2019 at 06:54:04AM +0800, Pingfan Liu wrote: > As for FOLL_LONGTERM, it is checked in the slow path > __gup_longterm_unlocked(). But it is not checked in the fast path, which > means a possible leak of CMA page to longterm pinned requirement through > this crack. > > Place a check in the fast path. > > Signed-off-by: Pingfan Liu > Cc: Ira Weiny > Cc: Andrew Morton > Cc: Mike Rapoport > Cc: Dan Williams > Cc: Matthew Wilcox > Cc: John Hubbard > Cc: "Aneesh Kumar K.V" > Cc: Keith Busch > Cc: linux-kernel@vger.kernel.org > --- > mm/gup.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index f173fcb..00feab3 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2235,6 +2235,18 @@ int get_user_pages_fast(unsigned long start, int nr_pages, > local_irq_enable(); > ret = nr; > } > +#if defined(CONFIG_CMA) > + if (unlikely(gup_flags & FOLL_LONGTERM)) { > + int i, j; > + > + for (i = 0; i < nr; i++) > + if (is_migrate_cma_page(pages[i])) { > + for (j = i; j < nr; j++) > + put_page(pages[j]); Should be put_user_page() now. For now that just calls put_page() but it is slated to change soon. I also wonder if this would be more efficient as a check as we are walking the page tables and bail early. Perhaps the code complexity is not worth it? > + nr = i; Why not just break from the loop here? Or better yet just use 'i' in the inner loop... Ira > + } > + } > +#endif > > if (nr < nr_pages) { > /* Try to get the remaining pages with get_user_pages */ > -- > 2.7.5 >