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From 8f412efbb8bb57fde0f924a7ad084f1c536c4a0b Mon Sep 17 00:00:00 2001
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From: Fam Zheng <famz@redhat.com>
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Date: Tue, 20 Jan 2015 03:42:13 +0100
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Subject: [PATCH 06/16] iscsi: Refuse to open as writable if the LUN is write
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 protected
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Message-id: <1421725333-27072-1-git-send-email-famz@redhat.com>
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Patchwork-id: 63370
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O-Subject: [RHEL-7.2 qemu-kvm PATCH v2] iscsi: Refuse to open as writable if the LUN is write protected
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Bugzilla: 1032412
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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Before, when a write protected iSCSI target is attached as scsi-disk
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with BDRV_O_RDWR, we report it as writable, while in fact all writes
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will fail.
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One way to improve this is to report write protect flag as true to
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guest, but a even better way is to refuse using a write protected LUN to
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guest.
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Target write protect flag is checked with a mode sense query.
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Signed-off-by: Fam Zheng <famz@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit c1d4096b0f033d0a52c542f0948403783c3682e9)
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Signed-off-by: Fam Zheng <famz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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Conflicts:
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	block/iscsi.c
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Trivial context conflict: AioContext attach/detach functions are not
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present in downstream.
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---
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 block/iscsi.c | 43 +++++++++++++++++++++++++++++++++++++++++++
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 1 file changed, 43 insertions(+)
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diff --git a/block/iscsi.c b/block/iscsi.c
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index 4f42f29..3d61dd7 100644
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--- a/block/iscsi.c
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+++ b/block/iscsi.c
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@@ -1290,6 +1290,41 @@ fail:
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     return NULL;
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 }
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+
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+static bool iscsi_is_write_protected(IscsiLun *iscsilun)
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+{
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+    struct scsi_task *task;
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+    struct scsi_mode_sense *ms = NULL;
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+    bool wrprotected = false;
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+
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+    task = iscsi_modesense6_sync(iscsilun->iscsi, iscsilun->lun,
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+                                 1, SCSI_MODESENSE_PC_CURRENT,
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+                                 0x3F, 0, 255);
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+    if (task == NULL) {
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+        error_report("iSCSI: Failed to send MODE_SENSE(6) command: %s",
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+                     iscsi_get_error(iscsilun->iscsi));
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+        goto out;
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+    }
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+
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+    if (task->status != SCSI_STATUS_GOOD) {
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+        error_report("iSCSI: Failed MODE_SENSE(6), LUN assumed writable");
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+        goto out;
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+    }
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+    ms = scsi_datain_unmarshall(task);
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+    if (!ms) {
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+        error_report("iSCSI: Failed to unmarshall MODE_SENSE(6) data: %s",
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+                     iscsi_get_error(iscsilun->iscsi));
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+        goto out;
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+    }
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+    wrprotected = ms->device_specific_parameter & 0x80;
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+
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+out:
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+    if (task) {
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+        scsi_free_scsi_task(task);
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+    }
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+    return wrprotected;
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+}
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+
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 /*
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  * We support iscsi url's on the form
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  * iscsi://[<username>%<password>@]<host>[:<port>]/<targetname>/<lun>
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@@ -1405,6 +1440,14 @@ static int iscsi_open(BlockDriverState *bs, QDict *options, int flags,
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     scsi_free_scsi_task(task);
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     task = NULL;
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+    /* Check the write protect flag of the LUN if we want to write */
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+    if (iscsilun->type == TYPE_DISK && (flags & BDRV_O_RDWR) &&
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+        iscsi_is_write_protected(iscsilun)) {
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+        error_setg(errp, "Cannot open a write protected LUN as read-write");
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+        ret = -EACCES;
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+        goto out;
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+    }
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+
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     iscsi_readcapacity_sync(iscsilun, &local_err);
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     if (local_err != NULL) {
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         error_propagate(errp, local_err);
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-- 
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1.8.3.1
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