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Tue, 13 Apr 2021 09:23:49 -0400 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-431-wLJBZuGgNfCJooX-Id01ZA-1; Tue, 13 Apr 2021 09:23:38 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 46D8280A1AC; Tue, 13 Apr 2021 13:23:34 +0000 (UTC) Received: from merkur.fritz.box (ovpn-112-130.phx2.redhat.com [10.3.112.130]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3CA0560936; Tue, 13 Apr 2021 13:23:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618320222; 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; bh=uJi3njPjBzXWyT8wQ0qEIDADpPciwKn7G6LxVcptVQA=; b=GxqvXWHds6xnxLw4s2zVnw6rWHS2aZqj0Z4wNlkxLNupFXvLaqG3QxFXwfScNuiZx9ULrG rnEzY9uNPOM2PgRepfGx+hKqKhBBbLvBWkV+dNreQis0P7EVPyNs1P9wBcdwOXlcrlhwtS kv7yDewGMLBFp0HpChqa8/sVyXjKH30= X-MC-Unique: wLJBZuGgNfCJooX-Id01ZA-1 From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PATCH 2/2] qemu-img convert: Unshare write permission for source Date: Tue, 13 Apr 2021 15:23:24 +0200 Message-Id: <20210413132324.24043-3-kwolf@redhat.com> In-Reply-To: <20210413132324.24043-1-kwolf@redhat.com> References: <20210413132324.24043-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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, xuwei@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" For a successful conversion of an image, we must make sure that its content doesn't change during the conversion. A special case of this is using the same image file both as the source and as the destination. If both input and output format are raw, the operation would just be useless work, with other formats it is a sure way to destroy the image. This will now fail because the image file can't be opened a second time for the output when opening it for the input has already acquired file locks to unshare BLK_PERM_WRITE. Nevertheless, if there is some reason in a special case why it is actually okay to allow writes to the image while it is being converted, -U can still be used to force sharing all permissions. Note that for most image formats, BLK_PERM_WRITE would already be unshared by the format driver, so this only really makes a difference for raw source images (but any output format). Reported-by: Xueqiang Wei Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake --- qemu-img.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/qemu-img.c b/qemu-img.c index babb5573ab..a5993682aa 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -2146,7 +2146,7 @@ static void set_rate_limit(BlockBackend *blk, int64_t= rate_limit) =20 static int img_convert(int argc, char **argv) { - int c, bs_i, flags, src_flags =3D 0; + int c, bs_i, flags, src_flags =3D BDRV_O_NO_SHARE; const char *fmt =3D NULL, *out_fmt =3D NULL, *cache =3D "unsafe", *src_cache =3D BDRV_DEFAULT_CACHE, *out_baseimg =3D NULL, *out_filename, *out_baseimg_param, *snapshot_name =3D NULL; --=20 2.30.2