From patchwork Mon Feb 27 20:09:36 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 733140 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3vXD2z6Wq8z9s8N for ; Tue, 28 Feb 2017 07:34:35 +1100 (AEDT) Received: from localhost ([::1]:56645 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciS09-00045H-An for incoming@patchwork.ozlabs.org; Mon, 27 Feb 2017 15:34:33 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57690) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciRdq-0000cx-Ok for qemu-devel@nongnu.org; Mon, 27 Feb 2017 15:11:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ciRdp-0003kj-Af for qemu-devel@nongnu.org; Mon, 27 Feb 2017 15:11:30 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36572) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ciRdm-0003js-6K; Mon, 27 Feb 2017 15:11:26 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6741E61B85; Mon, 27 Feb 2017 20:11:26 +0000 (UTC) Received: from noname.redhat.com (ovpn-116-148.ams2.redhat.com [10.36.116.148]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id v1RK9n8m003294; Mon, 27 Feb 2017 15:11:24 -0500 From: Kevin Wolf To: qemu-block@nongnu.org Date: Mon, 27 Feb 2017 21:09:36 +0100 Message-Id: <1488226184-9044-36-git-send-email-kwolf@redhat.com> In-Reply-To: <1488226184-9044-1-git-send-email-kwolf@redhat.com> References: <1488226184-9044-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Mon, 27 Feb 2017 20:11:26 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v2 35/43] hmp: Request permissions in qemu-io X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, jcody@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" The HMP command 'qemu-io' is a bit tricky because it wants to work on the original BlockBackend, but additional permissions could be required. The details are explained in a comment in the code, but in summary, just request whatever permissions the current qemu-io command needs. Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz --- block/block-backend.c | 6 ++++++ hmp.c | 26 +++++++++++++++++++++++++- include/qemu-io.h | 1 + include/sysemu/block-backend.h | 1 + qemu-io-cmds.c | 28 ++++++++++++++++++++++++++++ 5 files changed, 61 insertions(+), 1 deletion(-) diff --git a/block/block-backend.c b/block/block-backend.c index 38a3858..daa7908 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -584,6 +584,12 @@ int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm, return 0; } +void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm) +{ + *perm = blk->perm; + *shared_perm = blk->shared_perm; +} + static int blk_do_attach_dev(BlockBackend *blk, void *dev) { if (blk->dev) { diff --git a/hmp.c b/hmp.c index e219f97..7b44e64 100644 --- a/hmp.c +++ b/hmp.c @@ -2051,7 +2051,6 @@ void hmp_qemu_io(Monitor *mon, const QDict *qdict) if (!blk) { BlockDriverState *bs = bdrv_lookup_bs(NULL, device, &err); if (bs) { - /* FIXME Use real permissions */ blk = local_blk = blk_new(0, BLK_PERM_ALL); ret = blk_insert_bs(blk, bs, &err); if (ret < 0) { @@ -2065,6 +2064,31 @@ void hmp_qemu_io(Monitor *mon, const QDict *qdict) aio_context = blk_get_aio_context(blk); aio_context_acquire(aio_context); + /* + * Notably absent: Proper permission management. This is sad, but it seems + * almost impossible to achieve without changing the semantics and thereby + * limiting the use cases of the qemu-io HMP command. + * + * In an ideal world we would unconditionally create a new BlockBackend for + * qemuio_command(), but we have commands like 'reopen' and want them to + * take effect on the exact BlockBackend whose name the user passed instead + * of just on a temporary copy of it. + * + * Another problem is that deleting the temporary BlockBackend involves + * draining all requests on it first, but some qemu-iotests cases want to + * issue multiple aio_read/write requests and expect them to complete in + * the background while the monitor has already returned. + * + * This is also what prevents us from saving the original permissions and + * restoring them later: We can't revoke permissions until all requests + * have completed, and we don't know when that is nor can we really let + * anything else run before we have revoken them to avoid race conditions. + * + * What happens now is that command() in qemu-io-cmds.c can extend the + * permissions if necessary for the qemu-io command. And they simply stay + * extended, possibly resulting in a read-only guest device keeping write + * permissions. Ugly, but it appears to be the lesser evil. + */ qemuio_command(blk, command); aio_context_release(aio_context); diff --git a/include/qemu-io.h b/include/qemu-io.h index 4d402b9..196fde0 100644 --- a/include/qemu-io.h +++ b/include/qemu-io.h @@ -36,6 +36,7 @@ typedef struct cmdinfo { const char *args; const char *oneline; helpfunc_t help; + uint64_t perm; } cmdinfo_t; extern bool qemuio_misalign; diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h index b23f683..096c17f 100644 --- a/include/sysemu/block-backend.h +++ b/include/sysemu/block-backend.h @@ -107,6 +107,7 @@ bool bdrv_has_blk(BlockDriverState *bs); bool bdrv_is_root_node(BlockDriverState *bs); int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm, Error **errp); +void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm); void blk_set_allow_write_beyond_eof(BlockBackend *blk, bool allow); void blk_iostatus_enable(BlockBackend *blk); diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c index 7ac1576..2c48f9c 100644 --- a/qemu-io-cmds.c +++ b/qemu-io-cmds.c @@ -83,6 +83,29 @@ static int command(BlockBackend *blk, const cmdinfo_t *ct, int argc, } return 0; } + + /* Request additional permissions if necessary for this command. The caller + * is responsible for restoring the original permissions afterwards if this + * is what it wants. */ + if (ct->perm && blk_is_available(blk)) { + uint64_t orig_perm, orig_shared_perm; + blk_get_perm(blk, &orig_perm, &orig_shared_perm); + + if (ct->perm & ~orig_perm) { + uint64_t new_perm; + Error *local_err = NULL; + int ret; + + new_perm = orig_perm | ct->perm; + + ret = blk_set_perm(blk, new_perm, orig_shared_perm, &local_err); + if (ret < 0) { + error_report_err(local_err); + return 0; + } + } + } + optind = 0; return ct->cfunc(blk, argc, argv); } @@ -918,6 +941,7 @@ static const cmdinfo_t write_cmd = { .name = "write", .altname = "w", .cfunc = write_f, + .perm = BLK_PERM_WRITE, .argmin = 2, .argmax = -1, .args = "[-bcCfquz] [-P pattern] off len", @@ -1093,6 +1117,7 @@ static int writev_f(BlockBackend *blk, int argc, char **argv); static const cmdinfo_t writev_cmd = { .name = "writev", .cfunc = writev_f, + .perm = BLK_PERM_WRITE, .argmin = 2, .argmax = -1, .args = "[-Cfq] [-P pattern] off len [len..]", @@ -1392,6 +1417,7 @@ static int aio_write_f(BlockBackend *blk, int argc, char **argv); static const cmdinfo_t aio_write_cmd = { .name = "aio_write", .cfunc = aio_write_f, + .perm = BLK_PERM_WRITE, .argmin = 2, .argmax = -1, .args = "[-Cfiquz] [-P pattern] off len [len..]", @@ -1556,6 +1582,7 @@ static const cmdinfo_t truncate_cmd = { .name = "truncate", .altname = "t", .cfunc = truncate_f, + .perm = BLK_PERM_WRITE | BLK_PERM_RESIZE, .argmin = 1, .argmax = 1, .args = "off", @@ -1653,6 +1680,7 @@ static const cmdinfo_t discard_cmd = { .name = "discard", .altname = "d", .cfunc = discard_f, + .perm = BLK_PERM_WRITE, .argmin = 2, .argmax = -1, .args = "[-Cq] off len",