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[209.85.220.65]) by mx.google.com with SMTPS id p2sor350098wma.27.2019.06.24.14.02.07 for (Google Transport Security); Mon, 24 Jun 2019 14:02:07 -0700 (PDT) Received-SPF: pass (google.com: domain of jgg@ziepe.ca designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@ziepe.ca header.s=google header.b=i+h5jdKO; spf=pass (google.com: domain of jgg@ziepe.ca designates 209.85.220.65 as permitted sender) smtp.mailfrom=jgg@ziepe.ca DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Y7+HSfyIPKIyVRlHiPSUTXfMPMA2cBMnzwF3/BJJWoM=; b=i+h5jdKODrJM6HAgihfib7r1p3HTIoXotHgwp0BCzd39jXyo1BGTDGN5CpLNMF70TR V6PVWeRW3fvAO6anYPbAasncAm2gfDig99onMjq8DGbcxmOsbdJoUx+UOv3Ew172buN4 Vpsbiiy/5q+1oRn8UdTlfhMTuBnx4G1ji+wcVIaoYK5Nbt5H8mqxT5v/JzerbsooORD5 HimcJCbD82rblSOa3TsdNlNx3R6AxGDFuxuK+lEyTuOggfGhT5ua5kBPNLimVjJkqu5U RIddsbNK0RH7LIGRspoDR8r0YYISQuOycZZHVH/0xfxFXODjXkabiQ3hMa0QYuximxJ6 o2Mg== X-Google-Smtp-Source: APXvYqxYsEWfPj+ojP/Pdo0/oemDCD+9/xSgl5N/QS6OZzqvHa256HMQOw+3zV/4M5gAiwA2ZCoPBA== X-Received: by 2002:a1c:228b:: with SMTP id i133mr17321325wmi.140.1561410126760; Mon, 24 Jun 2019 14:02:06 -0700 (PDT) Received: from ziepe.ca ([66.187.232.66]) by smtp.gmail.com with ESMTPSA id k125sm600943wmf.41.2019.06.24.14.02.02 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 24 Jun 2019 14:02:02 -0700 (PDT) Received: from jgg by jggl.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hfW6D-0001Mv-3O; Mon, 24 Jun 2019 18:02:01 -0300 From: Jason Gunthorpe To: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com Cc: linux-rdma@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Ben Skeggs , Christoph Hellwig , Philip Yang , Ira Weiny , Jason Gunthorpe , Souptick Joarder Subject: [PATCH v4 hmm 10/12] mm/hmm: Poison hmm_range during unregister Date: Mon, 24 Jun 2019 18:01:08 -0300 Message-Id: <20190624210110.5098-11-jgg@ziepe.ca> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190624210110.5098-1-jgg@ziepe.ca> References: <20190624210110.5098-1-jgg@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: From: Jason Gunthorpe Trying to misuse a range outside its lifetime is a kernel bug. Use poison bytes to help detect this condition. Double unregister will reliably crash. Signed-off-by: Jason Gunthorpe Reviewed-by: Jérôme Glisse Reviewed-by: John Hubbard Acked-by: Souptick Joarder Reviewed-by: Ralph Campbell Reviewed-by: Ira Weiny Tested-by: Philip Yang --- v2 - Keep range start/end valid after unregistration (Jerome) v3 - Revise some comments (John) - Remove start/end WARN_ON (Souptick) v4 - Fix tabs vs spaces in comment (Christoph) --- mm/hmm.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index 2ef14b2b5505f6..c30aa9403dbe4d 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -925,19 +925,21 @@ 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) - return; - mutex_lock(&hmm->lock); list_del_init(&range->list); mutex_unlock(&hmm->lock); /* Drop reference taken by hmm_range_register() */ - range->valid = false; mmput(hmm->mm); hmm_put(hmm); - range->hmm = NULL; + + /* + * The range is now invalid and the ref on the hmm is dropped, so + * poison the pointer. Leave other fields in place, for the caller's + * use. + */ + range->valid = false; + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm)); } EXPORT_SYMBOL(hmm_range_unregister); -- 2.22.0