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 X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7AC4C0044D for ; Mon, 16 Mar 2020 19:04:29 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7A8F420658 for ; Mon, 16 Mar 2020 19:04:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Yr3EPKCc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7A8F420658 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:47054 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jDv2K-0007ip-MH for qemu-devel@archiver.kernel.org; Mon, 16 Mar 2020 15:04:28 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35184) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jDu72-0001p9-NE for qemu-devel@nongnu.org; Mon, 16 Mar 2020 14:05:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jDu70-0006FP-Uj for qemu-devel@nongnu.org; Mon, 16 Mar 2020 14:05:16 -0400 Received: from us-smtp-delivery-74.mimecast.com ([216.205.24.74]:59562) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jDu70-00065s-MW for qemu-devel@nongnu.org; Mon, 16 Mar 2020 14:05:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584381913; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=AA9WE02bRISwyYhv61zFnoOLqnvNnoeCfrmZVc2rCIU=; b=Yr3EPKCcliJ/SpIeof+Pf3Kbwn7DDP4S+Iw7Sk8rGh7AfvDPIe8Yn4K4NrFC8KEray04J0 /mLPxDZsSYHJWq9k2ybNhG6rnOihz8QsrEJoCREXwDDWp7X5uG6bvvIWE1+sjcEpqEVivZ 8pA1th5ehwckjiOfCWabtPCZfY+/bTQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-29-9xxP8mXhPfisiSx0XracoA-1; Mon, 16 Mar 2020 14:05:12 -0400 X-MC-Unique: 9xxP8mXhPfisiSx0XracoA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7FCC292BB85; Mon, 16 Mar 2020 17:48:14 +0000 (UTC) Received: from [10.10.125.118] (ovpn-125-118.rdu2.redhat.com [10.10.125.118]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5F3295D9E2; Mon, 16 Mar 2020 17:48:13 +0000 (UTC) Subject: Re: [PATCH 2/2] block/qcow2: zero data_file child after free To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20200316060631.30052-1-vsementsov@virtuozzo.com> <20200316060631.30052-3-vsementsov@virtuozzo.com> From: John Snow Autocrypt: addr=jsnow@redhat.com; prefer-encrypt=mutual; keydata= mQINBFTKefwBEAChvwqYC6saTzawbih87LqBYq0d5A8jXYXaiFMV/EvMSDqqY4EY6whXliNO IYzhgrPEe7ZmPxbCSe4iMykjhwMh5byIHDoPGDU+FsQty2KXuoxto+ZdrP9gymAgmyqdk3aV vzzmCa3cOppcqKvA0Kqr10UeX/z4OMVV390V+DVWUvzXpda45/Sxup57pk+hyY52wxxjIqef rj8u5BN93s5uCVTus0oiVA6W+iXYzTvVDStMFVqnTxSxlpZoH5RGKvmoWV3uutByQyBPHW2U 1Y6n6iEZ9MlP3hcDqlo0S8jeP03HaD4gOqCuqLceWF5+2WyHzNfylpNMFVi+Hp0H/nSDtCvQ ua7j+6Pt7q5rvqgHvRipkDDVsjqwasuNc3wyoHexrBeLU/iJBuDld5iLy+dHXoYMB3HmjMxj 3K5/8XhGrDx6BDFeO3HIpi3u2z1jniB7RtyVEtdupED6lqsDj0oSz9NxaOFZrS3Jf6z/kHIf h42mM9Sx7+s4c07N2LieUxcfqhFTaa/voRibF4cmkBVUhOD1AKXNfhEsTvmcz9NbUchCkcvA T9119CrsxfVsE7bXiGvdXnzyGLXdsoosjzwacKdOrVaDmN3Uy+SHiQXo6TlkSdV0XH2PUxTM LsBFIO9qXO43Ai6J6iPAP/01l8fuZfpJE0/L/c25yyaND7xA3wARAQABtCpKb2huIFNub3cg KEpvaG4gSHVzdG9uKSA8anNub3dAcmVkaGF0LmNvbT6JAlQEEwECAD4CGwMCHgECF4AFCwkI BwMFFQoJCAsFFgIDAQAWIQT665cRoSz0dYEvGPKIqQZNGDVh6wUCXF392gUJC1Xq3gAKCRCI qQZNGDVh6558D/9pM4pu4njX5aT6uUW3vAmbWLF1jfPxiTQgSHAnm9EBMZED/fsvkzj97clo LN7JKmbYZNgJmR01A7flG45V4iOR/249qAfaVuD+ZzZi1R4jFzr13WS+IEdn0hYp9ITndb7R ezW+HGu6/rP2PnfmDnNowgJu6Dp6IUEabq8SXXwGHXZPuMIrsXJxUdKJdGnh1o2u7271yNO7 J9PEMuMDsgjsdnaGtv7aQ9CECtXvBleAc06pLW2HU10r5wQyBMZGITemJdBhhdzGmbHAL0M6 vKi/bafHRWqfMqOAdDkv3Jg4arl2NCG/uNateR1z5e529+UlB4XVAQT+f5T/YyI65DFTY940 il3aZhA8u788jZEPMXmt94u7uPZbEYp7V0jt68SrTaOgO7NaXsboXFjwEa42Ug5lB5d5/Qdp 1AITUv0NJ51kKwhHL1dEagGeloIsGVQILmpS0MLdtitBHqZLsnJkRvtMaxo47giyBlv2ewmq tIGTlVLxHx9xkc9aVepOuiGlZaZB72c9AvZs9rKaAjgU2UfJHlB/Hr4uSk/1EY0IgMv4vnsG 1sA5gvS7A4T4euu0PqHtn2sZEWDrk5RDbw0yIb53JYdXboLFmFXKzVASfKh2ZVeXRBlQQSJi 3PBR1GzzqORlfryby7mkY857xzCI2NkIkD2eq+HhzFTfFOTdGrkCDQRUynn8ARAAwbhP45BE d/zAMBPV2dk2WwIwKRSKULElP3kXpcuiDWYQob3UODUUqClO+3aXVRndaNmZX9WbzGYexVo3 5j+CVBCGr3DlU8AL9pp3KQ3SJihWcDed1LSmUf8tS+10d6mdGxDqgnd/OWU214isvhgWZtZG MM/Xj7cx5pERIiP+jqu7PT1cibcfcEKhPjYdyV1QnLtKNGrTg/UMKaL+qkWBUI/8uBoa0HLs NH63bXsRtNAG8w6qG7iiueYZUIXKc4IHINUguqYQJVdSe+u8b2N5XNhDSEUhdlqFYraJvX6d TjxMTW5lzVG2KjztfErRNSUmu2gezbw1/CV0ztniOKDA7mkQi6UIUDRh4LxRm5mflfKiCyDQ L6P/jxHBxFv+sIgjuLrfNhIC1p3z9rvCh+idAVJgtHtYl8p6GAVrF+4xQV2zZH45tgmHo2+S JsLPjXZtWVsWANpepXnesyabWtNAV4qQB7/SfC77zZwsVX0OOY2Qc+iohmXo8U7DgXVDgl/R /5Qgfnlv0/3rOdMt6ZPy5LJr8D9LJmcP0RvX98jyoBOf06Q9QtEwJsNLCOCo2LKNL71DNjZr nXEwjUH66CXiRXDbDKprt71BiSTitkFhGGU88XCtrp8R9yArXPf4MN+wNYBjfT7K29gWTzxt 9DYQIvEf69oZD5Z5qHYGp031E90AEQEAAYkCPAQYAQIAJgIbDBYhBPrrlxGhLPR1gS8Y8oip Bk0YNWHrBQJcXf3JBQkLVerNAAoJEIipBk0YNWHrU1AP/1FOK2SBGbyhHa5vDHuf47fgLipC e0/h1E0vdSonzlhPxuZoQ47FjzG9uOhqqQG6/PqtWs/FJIyz8aGG4aV+pSA/9Ko3/2ND8MSY ZflWs7Y8Peg08Ro01GTHFITjEUgHpTpHiT6TNcZB5aZNJ8jqCtW5UlqvXXbVeSTmO70ZiVtc vUJbpvSxYmzhFfZWaXIPcNcKWL1rnmnzs67lDhMLdkYVf91aml/XtyMUlfB8Iaejzud9Ht3r C0pA9MG57pLblX7okEshxAC0+tUdY2vANWFeX0mgqRt1GSuG9XM9H/cKP1czfUV/FgaWo/Ya fM4eMhUAlL/y+/AJxxumPhBXftM4yuiktp2JMezoIMJI9fmhjfWDw7+2jVrx9ze1joLakFD1 rVAoHxVJ7ORfQ4Ni/qWbQm3T6qQkSMt4N/scNsMczibdTPxU7qtwQwIeFOOc3wEwmJ9Qe3ox TODQ0agXiWVj0OXYCHJ6MxTDswtyTGQW+nUHpKBgHGwUaR6d1kr/LK9+5LpOfRlK9VRfEu7D PGNiRkr8Abp8jHsrBqQWfUS1bAf62bq6XUel0kUCtb7qCq024aOczXYWPFpJFX+nhp4d7NeH Edq+wlC13sBSiSHC7T5yssJ+7JPa2ATLlSKhEvBsLe2TsSTTtFlA0nBclqhfJXzimiuge9qU E40lvMWBuQINBFTKimUBEADDbJ+pQ5M4QBMWkaWImRj7c598xIZ37oKM6rGaSnuB1SVb7YCr Ci2MTwQcrQscA2jm80O8VFqWk+/XsEp62dty47GVwSfdGje/3zv3VTH2KhOCKOq3oPP5ZXWY rz2d2WnTvx++o6lU7HLHDEC3NGLYNLkL1lyVxLhnhvcMxkf1EGA1DboEcMgnJrNB1pGP27ww cSfvdyPGseV+qZZa8kuViDga1oxmnYDxFKMGLxrClqHrRt8geQL1Wj5KFM5hFtGTK4da5lPn wGNd6/CINMeCT2AWZY5ySz7/tSZe5F22vPvVZGoPgQicYWdNc3ap7+7IKP86JNjmec/9RJcz jvrYjJdiqBVldXou72CtDydKVLVSKv8c2wBDJghYZitfYIaL8cTvQfUHRYTfo0n5KKSec8Vo vjDuxmdbOUBA+SkRxqmneP5OxGoZ92VusrwWCjry8HRsNdR+2T+ClDCO6Wpihu4V3CPkQwTy eCuMHPAT0ka5paTwLrnZIxsdfnjUa96T10vzmQgAxpbbiaLvgKJ8+76OPdDnhddyxd2ldYfw RkF5PEGg3mqZnYKNNBtwjvX49SAvgETQvLzQ8IKVgZS0m4z9qHHvtc1BsQnFfe+LJOFjzZr7 CrDNJMqk1JTHYsSi2JcN3vY32WMezXSQ0TzeMK4kdnclSQyp/h23GWod5QARAQABiQRbBBgB AgAmAhsCFiEE+uuXEaEs9HWBLxjyiKkGTRg1YesFAlxd/coFCQtV2mQCKcFdIAQZAQIABgUC VMqKZQAKCRB974EGqvw5DiJoEACLmuiRq9ifvOh5DyBFwRS7gvA14DsGQngmC57EzV0EFcfM XVi1jX5OtwUyUe0Az5r6lHyyHDsDsIpLKBlWrYCeLpUhRR3oy181T7UNxvujGFeTkzvLAOo6 Hs3b8Wv9ARg+7acRYkQRNY7k0GIJ6YZz149tRyRKAy/vSjsaB9Lt0NOd1wf2EQMKwRVELwJD y0AazGn+0PRP7Bua2YbtxaBmhBBDb2tPpwn8U9xdckB4Vlft9lcWNsC/18Gi9bpjd9FSbdH/ sOUI+3ToWYENeoT4IP09wn6EkgWaJS3nAUN/MOycNej2i4Yhy2wDDSKyTAnVkSSSoXk+tK91 HfqtokbDanB8daP+K5LgoiWHzjfWzsxA2jKisI4YCGjrYQzTyGOT6P6u6SEeoEx10865B/zc 8/vN50kncdjYz2naacIDEKQNZlnGLsGkpCbfmfdi3Zg4vuWKNdWr0wGUzDUcpqW0y/lUXna+ 6uyQShX5e4JD2UPuf9WAQ9HtgSAkaDd4O1I2J41sleePzZOVB3DmYgy+ECRJJ5nw3ihdxpgc y/v3lfcJaqiyCv0PF+K/gSOvwhH7CbVqARmptT7yhhxqFdaYWo2Z2ksuKyoKSRMFCXQY5oac uTmyPIT4STFyUQFeqSCWDum/NFNoSKhmItw2Td+4VSJHShRVbg39KNFPZ7mXYAkQiKkGTRg1 YesWJA/+PV3qDUtPNEGwjVvjQqHSbrBy94tu6gJvPHgGPtRDYvxnCaJsmgiC0pGB2KFRsnfl 2zBNBEWF/XwsI081jQE5UO60GKmHTputChLXpVobyuc+lroG2YhknXRBAV969SLnZR4BS/1s Gi046gOXfaKYatve8BiZr5it5Foq3FMPDNgZMit1H9Dk8rkKFfDMRf8EGS/Z+TmyEsIf99H7 TH3n7lco8qO81fSFwkh4pvo2kWRFYTC5vsIVQ+GqVUp+W1DZJHxX8LwWuF1AzUt4MUTtNAvy TXl5EgsmoY9mpNNL7ZnW65oG63nEP5KNiybvuQJzXVxR8eqzOh2Mod4nHg3PE7UCd3DvLNsn GXFRo44WyT/G2lArBtjpkut7bDm0i1nENABy2UgS+1QvdmgNu6aEZxdNthwRjUhuuvCCDMA4 rCDQYyakH2tJNQgkXkeLodBKF4bHiBbuwj0E39S9wmGgg+q4OTnAO/yhQGknle7a7G5xHBwE i0HjnLoJP5jDcoMTabZTIazXmJz3pKM11HYJ5/ZsTIf3ZRJJKIvXJpbmcAPVwTZII6XxiJdh RSSX4Mvd5pL/+5WI6NTdW6DMfigTtdd85fe6PwBNVJL2ZvBfsBJZ5rxg1TOH3KLsYBqBTgW2 glQofxhkJhDEcvjLhe3Y2BlbCWKOmvM8XS9TRt0OwUs= Message-ID: Date: Mon, 16 Mar 2020 13:48:12 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200316060631.30052-3-vsementsov@virtuozzo.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 216.205.24.74 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, den@openvz.org, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/16/20 2:06 AM, Vladimir Sementsov-Ogievskiy wrote: > data_file being NULL doesn't seem to be a correct state, but it's > better than dead pointer and simpler to debug. > How important is it to have correct state in the middle of teardown? > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > block/qcow2.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/block/qcow2.c b/block/qcow2.c > index d44b45633d..6cdefe059f 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c > @@ -1758,6 +1758,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options, > g_free(s->image_data_file); > if (has_data_file(bs)) { > bdrv_unref_child(bs, s->data_file); > + s->data_file = NULL; > } Probably OK to set to NULL, since this is at the end of a failed open where it would have been set for the first time anyway. It's an invalid state, but resulting from a failed call. I think that's OK. (Are there any callers of bdrv_open or qcow2_open that don't just immediately trash this object if it failed? I don't know of any, but there's a lot of callers to bdrv_open.) > g_free(s->unknown_header_fields); > cleanup_unknown_header_ext(bs); > @@ -2621,6 +2622,7 @@ static void qcow2_close(BlockDriverState *bs) > > if (has_data_file(bs)) { > bdrv_unref_child(bs, s->data_file); > + s->data_file = NULL; > } > Probably fine here too. I can't imagine it's valid to use this object after close() ... unless we open it again, and that should handle setting this back to a realistic value. > qcow2_refcount_close(bs); > So I think this is fine? If I understand right this just makes failures more obvious if we do accidentally use this value after a failed open or close, so that seems fine. Reviewed-by: John Snow (As always, I'll rely on block maintainers to do more serious structural review for cases I am not aware of)