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[70.62.41.24]) by smtp.gmail.com with ESMTPSA id l18-v6sm6200475iob.24.2018.11.13.07.40.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 13 Nov 2018 07:40:39 -0800 (PST) Subject: Re: [PATCH RFC] btrfs: harden agaist duplicate fsid To: dsterba@suse.cz, Anand Jain , linux-btrfs@vger.kernel.org References: <1538384164-3030-1-git-send-email-anand.jain@oracle.com> <98cd974b-d817-c30b-5cd7-d69214f44f39@gmail.com> <20181113153149.GD24115@twin.jikos.cz> From: "Austin S. Hemmelgarn" Message-ID: <00297772-cdaa-bcee-382b-02ff61bd0cae@gmail.com> Date: Tue, 13 Nov 2018 10:40:36 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20181113153149.GD24115@twin.jikos.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 11/13/2018 10:31 AM, David Sterba wrote: > On Mon, Oct 01, 2018 at 09:31:04PM +0800, Anand Jain wrote: >>>> +        /* >>>> +         * we are going to replace the device path, make sure its the >>>> +         * same device if the device mounted >>>> +         */ >>>> +        if (device->bdev) { >>>> +            struct block_device *path_bdev; >>>> + >>>> +            path_bdev = lookup_bdev(path); >>>> +            if (IS_ERR(path_bdev)) { >>>> +                mutex_unlock(&fs_devices->device_list_mutex); >>>> +                return ERR_CAST(path_bdev); >>>> +            } >>>> + >>>> +            if (device->bdev != path_bdev) { >>>> +                bdput(path_bdev); >>>> +                mutex_unlock(&fs_devices->device_list_mutex); >>>> +                return ERR_PTR(-EEXIST); >>> It would be _really_ nice to have an informative error message printed >>> here.  Aside from the possibility of an admin accidentally making a >>> block-level copy of the volume, >> >>> this code triggering could represent an >>> attempted attack against the system, so it's arguably something that >>> should be reported as happening. >> >>>   Personally, I think a WARN_ON_ONCE for >>> this would make sense, ideally per-volume if possible. >> >> Ah. Will add an warn. Thanks, Anand > > The requested error message is not in the patch you posted or I have > missed that (https://patchwork.kernel.org/patch/10641041/) . > > Austin, is the following ok for you? > > "BTRFS: duplicate device fsid:devid for %pU:%llu old:%s new:%s\n" > > BTRFS: duplicate device fsid:devid 7c667b96-59eb-43ad-9ae9-c878f6ad51d8:2 old:/dev/sda6 new:/dev/sdb6 > > As the UUID and paths are long I tried to squeeeze the rest so it's > still comprehensible but this would be better confirmed. Thanks. > Looks perfectly fine to me.