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From 8f412efbb8bb57fde0f924a7ad084f1c536c4a0b Mon Sep 17 00:00:00 2001
From: Fam Zheng <famz@redhat.com>
Date: Tue, 20 Jan 2015 03:42:13 +0100
Subject: [PATCH 06/16] iscsi: Refuse to open as writable if the LUN is write
 protected

Message-id: <1421725333-27072-1-git-send-email-famz@redhat.com>
Patchwork-id: 63370
O-Subject: [RHEL-7.2 qemu-kvm PATCH v2] iscsi: Refuse to open as writable if the LUN is write protected
Bugzilla: 1032412
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

Before, when a write protected iSCSI target is attached as scsi-disk
with BDRV_O_RDWR, we report it as writable, while in fact all writes
will fail.

One way to improve this is to report write protect flag as true to
guest, but a even better way is to refuse using a write protected LUN to
guest.

Target write protect flag is checked with a mode sense query.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit c1d4096b0f033d0a52c542f0948403783c3682e9)
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

Conflicts:
	block/iscsi.c

Trivial context conflict: AioContext attach/detach functions are not
present in downstream.
---
 block/iscsi.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/block/iscsi.c b/block/iscsi.c
index 4f42f29..3d61dd7 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -1290,6 +1290,41 @@ fail:
     return NULL;
 }
 
+
+static bool iscsi_is_write_protected(IscsiLun *iscsilun)
+{
+    struct scsi_task *task;
+    struct scsi_mode_sense *ms = NULL;
+    bool wrprotected = false;
+
+    task = iscsi_modesense6_sync(iscsilun->iscsi, iscsilun->lun,
+                                 1, SCSI_MODESENSE_PC_CURRENT,
+                                 0x3F, 0, 255);
+    if (task == NULL) {
+        error_report("iSCSI: Failed to send MODE_SENSE(6) command: %s",
+                     iscsi_get_error(iscsilun->iscsi));
+        goto out;
+    }
+
+    if (task->status != SCSI_STATUS_GOOD) {
+        error_report("iSCSI: Failed MODE_SENSE(6), LUN assumed writable");
+        goto out;
+    }
+    ms = scsi_datain_unmarshall(task);
+    if (!ms) {
+        error_report("iSCSI: Failed to unmarshall MODE_SENSE(6) data: %s",
+                     iscsi_get_error(iscsilun->iscsi));
+        goto out;
+    }
+    wrprotected = ms->device_specific_parameter & 0x80;
+
+out:
+    if (task) {
+        scsi_free_scsi_task(task);
+    }
+    return wrprotected;
+}
+
 /*
  * We support iscsi url's on the form
  * iscsi://[<username>%<password>@]<host>[:<port>]/<targetname>/<lun>
@@ -1405,6 +1440,14 @@ static int iscsi_open(BlockDriverState *bs, QDict *options, int flags,
     scsi_free_scsi_task(task);
     task = NULL;
 
+    /* Check the write protect flag of the LUN if we want to write */
+    if (iscsilun->type == TYPE_DISK && (flags & BDRV_O_RDWR) &&
+        iscsi_is_write_protected(iscsilun)) {
+        error_setg(errp, "Cannot open a write protected LUN as read-write");
+        ret = -EACCES;
+        goto out;
+    }
+
     iscsi_readcapacity_sync(iscsilun, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
-- 
1.8.3.1