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Sun, 13 Sep 2020 12:03:48 -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-46-9KgSBD1sM4ultvOg8vzbPg-1; Sun, 13 Sep 2020 12:03:42 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2F1551005E63; Sun, 13 Sep 2020 16:03:41 +0000 (UTC) Received: from localhost.localdomain (unknown [10.35.206.72]) by smtp.corp.redhat.com (Postfix) with ESMTP id E56D919C4F; Sun, 13 Sep 2020 16:03:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600013025; 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=z5U6NpADpwbz6hmsrwp+fNTljpdFoEsRxAFNUR7QhDM=; b=FtWqPkIpPSBjs56qhp/lLKDHerpKhYeQgm7e7/hr6Arpd84yhPT+udX3+tVja6uWFuuUZQ CjxxbJ0EZgMo9zoVI+o4Dk4qNpDu1WGldrixn7sVMquBHSfdImgGQ+4CeZ8rR6U9AKbbWL dcS5ROumZ5GLh1lkH6lfJrwAftZJkqc= X-MC-Unique: 9KgSBD1sM4ultvOg8vzbPg-1 From: Maxim Levitsky To: qemu-devel@nongnu.org Subject: [PATCH v5 9/9] scsi/scsi_bus: fix races in REPORT LUNS Date: Sun, 13 Sep 2020 19:02:59 +0300 Message-Id: <20200913160259.32145-10-mlevitsk@redhat.com> In-Reply-To: <20200913160259.32145-1-mlevitsk@redhat.com> References: <20200913160259.32145-1-mlevitsk@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlevitsk@redhat.com X-Mimecast-Spam-Score: 0.001 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=205.139.110.61; envelope-from=mlevitsk@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/13 11:28:09 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -37 X-Spam_score: -3.8 X-Spam_bar: --- X-Spam_report: (-3.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.695, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: Fam Zheng , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Eduardo Habkost , "Michael S. Tsirkin" , Maxim Levitsky , Stefan Hajnoczi , Paolo Bonzini Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" Currently scsi_target_emulate_report_luns iterates over the child device li= st twice, and there is no guarantee that this list is the same in both iterati= ons. The reason for iterating twise is that the first iteration calculates how much memory to allocate. However if we use a dynamic array we can avoid iterating twice, and therefo= re we avoid this race. Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=3D1866707 Signed-off-by: Maxim Levitsky Reviewed-by: Stefan Hajnoczi --- hw/scsi/scsi-bus.c | 65 ++++++++++++++++++++++------------------------ 1 file changed, 31 insertions(+), 34 deletions(-) diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c index dfd503f7ef..84c145c724 100644 --- a/hw/scsi/scsi-bus.c +++ b/hw/scsi/scsi-bus.c @@ -439,19 +439,23 @@ struct SCSITargetReq { static void store_lun(uint8_t *outbuf, int lun) { if (lun < 256) { + /* Simple logical unit addressing method*/ + outbuf[0] =3D 0; outbuf[1] =3D lun; - return; + } else { + /* Flat space addressing method */ + outbuf[0] =3D 0x40 | (lun >> 8); + outbuf[1] =3D (lun & 255); } - outbuf[1] =3D (lun & 255); - outbuf[0] =3D (lun >> 8) | 0x40; } =20 static bool scsi_target_emulate_report_luns(SCSITargetReq *r) { BusChild *kid; - int i, len, n; int channel, id; - bool found_lun0; + uint8_t tmp[8] =3D {0}; + int len =3D 0; + GByteArray *buf; =20 if (r->req.cmd.xfer < 16) { return false; @@ -459,48 +463,41 @@ static bool scsi_target_emulate_report_luns(SCSITarge= tReq *r) if (r->req.cmd.buf[2] > 2) { return false; } + + /* reserve space for 63 LUNs*/ + buf =3D g_byte_array_sized_new(512); + channel =3D r->req.dev->channel; id =3D r->req.dev->id; - found_lun0 =3D false; - n =3D 0; =20 - rcu_read_lock(); + /* add size (will be updated later to correct value */ + g_byte_array_append(buf, tmp, 8); + len +=3D 8; =20 - QTAILQ_FOREACH_RCU(kid, &r->req.bus->qbus.children, sibling) { - DeviceState *qdev =3D kid->child; - SCSIDevice *dev =3D SCSI_DEVICE(qdev); + /* add LUN0 */ + g_byte_array_append(buf, tmp, 8); + len +=3D 8; =20 - if (dev->channel =3D=3D channel && dev->id =3D=3D id) { - if (dev->lun =3D=3D 0) { - found_lun0 =3D true; - } - n +=3D 8; - } - } - if (!found_lun0) { - n +=3D 8; - } - - scsi_target_alloc_buf(&r->req, n + 8); - - len =3D MIN(n + 8, r->req.cmd.xfer & ~7); - memset(r->buf, 0, len); - stl_be_p(&r->buf[0], n); - i =3D found_lun0 ? 8 : 16; + rcu_read_lock(); QTAILQ_FOREACH_RCU(kid, &r->req.bus->qbus.children, sibling) { DeviceState *qdev =3D kid->child; SCSIDevice *dev =3D SCSI_DEVICE(qdev); =20 - if (dev->channel =3D=3D channel && dev->id =3D=3D id) { - store_lun(&r->buf[i], dev->lun); - i +=3D 8; + if (dev->channel =3D=3D channel && dev->id =3D=3D id && dev->lun != =3D 0) { + store_lun(tmp, dev->lun); + g_byte_array_append(buf, tmp, 8); + len +=3D 8; } } - rcu_read_unlock(); =20 - assert(i =3D=3D n + 8); - r->len =3D len; + r->buf_len =3D len; + r->buf =3D g_byte_array_free(buf, FALSE); + r->len =3D MIN(len, r->req.cmd.xfer & ~7); + + /* store the LUN list length */ + stl_be_p(&r->buf[0], len - 8); + return true; } =20 --=20 2.26.2