From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 35123C25B06 for ; Sun, 14 Aug 2022 14:25:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Nu1E7AmmDIl2LFiTiOoUmoMGabBpkxzR1LmY2ZhmWkw=; b=lSjGdqEj9jxDZ+z0hUt4I2jug0 tP4/NxM6jgFpt6KYOkbWKH6Ug6KCybN9YB7lfpX/3NNNh6iJf8+D1o0vHm2nz9gwkHIj6EI32pCVF RnvwGkeNYVf/+GGxKzf+oyUknUEqUsEwu9Y7cAKkbqA2ILDwx8cd7h3xzrzHfIdR7qyx4l4BKkAfV rnUG922f6ny6YEZdbL+UXCCNOh9qQ3m5ksOv0a1H2Psdp5UBy5d0Wo1ijOzOyDteq7tStzyBJ7Vxd o3fGOMhAK3ecsb3WS8ybs9sbmfV0usSb81rsjSDjuGPBjfPO+ufUXWOzQzX+dyOBQ10XvYWdKLnYn nCjFO5WA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oNEXz-007409-0s; Sun, 14 Aug 2022 14:24:59 +0000 Received: from mail-pl1-f182.google.com ([209.85.214.182]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oNEXw-0073z6-6E for linux-nvme@lists.infradead.org; Sun, 14 Aug 2022 14:24:57 +0000 Received: by mail-pl1-f182.google.com with SMTP id p18so4461677plr.8 for ; Sun, 14 Aug 2022 07:24:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc; bh=Nu1E7AmmDIl2LFiTiOoUmoMGabBpkxzR1LmY2ZhmWkw=; b=u7jQDdnyItEnpZlyd1Hi5gar2h8feQmKL81iPEgvZqbyu9E0Ucg8vb8MRUHx0yNTnB xuRBYXmLaqTtHPm78H7hWu70jcBWyAVgfVTwoMYTsuAHHEoza4aJ06b7QxwPVK/Hbb3p ets+1AD6JhP+hPWU95SqCmzrWIHmegGeQvcjZ+0OlSb9A8KOqK0DdCJ1BtKetqrUTLzE qGzHlRlvLJlhJcrmEpEvWBAkt9GEQc09XybejWxBTQv0cmQrl75x1zls6bnx2z4z44Hc OYvM4tA8ShWqhCiAbmcY3Ivffsb7PmxH1SBldv/9v4y6hNbeu60ZlMGW7aQVF1Tpqxa2 OZAQ== X-Gm-Message-State: ACgBeo29cGFTRRFem+Hm31apwgrJRzQZEXFI8IqnBwlmsfJ84GuoXGBs y+sn42zT3oqjL970Qu2n6mI= X-Google-Smtp-Source: AA6agR5HCgWAcQjNp29LelwPDbPAB0mm64U/w5KM+jlUo+hz5aRdPoEqZyCP7VVUl818K/V7bQ1yRA== X-Received: by 2002:a17:902:6808:b0:170:9453:8203 with SMTP id h8-20020a170902680800b0017094538203mr12696076plk.24.1660487094199; Sun, 14 Aug 2022 07:24:54 -0700 (PDT) Received: from [192.168.3.217] ([98.51.102.78]) by smtp.gmail.com with ESMTPSA id f7-20020a623807000000b0052acb753b8bsm5156039pfa.158.2022.08.14.07.24.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 14 Aug 2022 07:24:53 -0700 (PDT) Message-ID: <9ec2e292-1e75-8ee2-a9fc-d5adfab92fbd@acm.org> Date: Sun, 14 Aug 2022 07:24:51 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] nvmet: Fix a use-after-free Content-Language: en-US To: Sagi Grimberg , Keith Busch Cc: Christoph Hellwig , linux-nvme@lists.infradead.org, stable@vger.kernel.org References: <20220812210317.2252051-1-bvanassche@acm.org> From: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220814_072456_251152_401CBE81 X-CRM114-Status: GOOD ( 12.96 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 8/14/22 04:45, Sagi Grimberg wrote: > On 8/13/22 00:03, Bart Van Assche wrote: >> @@ -745,9 +747,9 @@ static void __nvmet_req_complete(struct nvmet_req >> *req, u16 status) >>       trace_nvmet_req_complete(req); >> -    if (req->ns) >> -        nvmet_put_namespace(req->ns); >>       req->ops->queue_response(req); >> +    if (ns) >> +        nvmet_put_namespace(ns); > > Why did the put change position? > I'm not exactly clear what was used-after-free here.. Hi Sagi, Is my understanding correct that the NVMe target namespace owns the block device `req` is associated with and hence that the namespace reference count must only be dropped after dereferencing the `req` pointer has finished? This is what I found in the NVMe target code: * nvmet_put_namespace() decreases ns->ref. * Dropping the last ns->ref causes nvmet_destroy_namespace() to be called. That function completes ns->disable_done. * nvmet_ns_disable() waits on that completion and calls nvmet_ns_dev_disable(). * For a block device, nvmet_ns_dev_disable() calls blkdev_put(). * The last blkdev_put() call calls disk_release(). * disk_release() calls blk_put_queue(). * The last blk_put_queue() call calls blk_release_queue(). * blk_release_queue() frees struct request_queue. * blk_mq_complete_request_remote() dereferences req->q. Thanks, Bart.