[Qemu-devel] [PATCH for-4.1 0/2] fdc: Fix inserting read-only media in empty drive

[Qemu-devel] [PATCH for-4.1 0/2] fdc: Fix inserting read-only media in empty drive

[Kevin Wolf]

Kevin Wolf (2):
  fdc: Fix inserting read-only media in empty drive
  iotests/118: Test inserting a read-only medium

 hw/block/fdc.c             | 11 ++++++++---
 tests/qemu-iotests/118     |  6 +++++-
 tests/qemu-iotests/118.out |  4 ++--
 3 files changed, 15 insertions(+), 6 deletions(-)

-- 
2.20.1

[Qemu-devel] [PATCH for-4.1 1/2] fdc: Fix inserting read-only media in empty drive

[Kevin Wolf]

In order to insert a read-only medium (i.e. a read-only block node) to
the BlockBackend of a floppy drive, we must not have taken write
permissions on that BlockBackend, or the operation will fail with the
error message "Block node is read-only".

The device already takes care to remove all permissions when the medium
is ejected, but the state isn't correct if the drive is initially empty:
It uses blk_is_read_only() to check whether write permissions should be
taken, but this function returns false for empty BlockBackends in the
common case.

Fix floppy_drive_realize() to avoid taking write permissions if the
drive is empty.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 hw/block/fdc.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/hw/block/fdc.c b/hw/block/fdc.c
index 77af9979de..9b24cb9b85 100644
--- a/hw/block/fdc.c
+++ b/hw/block/fdc.c
@@ -514,6 +514,7 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp)
     FloppyDrive *dev = FLOPPY_DRIVE(qdev);
     FloppyBus *bus = FLOPPY_BUS(qdev->parent_bus);
     FDrive *drive;
+    bool read_only;
     int ret;
 
     if (dev->unit == -1) {
@@ -542,6 +543,12 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp)
         dev->conf.blk = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);
         ret = blk_attach_dev(dev->conf.blk, qdev);
         assert(ret == 0);
+
+        /* Don't take write permissions on an empty drive to allow attaching a
+         * read-only node later */
+        read_only = true;
+    } else {
+        read_only = !blk_bs(dev->conf.blk) || blk_is_read_only(dev->conf.blk);
     }
 
     blkconf_blocksizes(&dev->conf);
@@ -559,9 +566,7 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp)
     dev->conf.rerror = BLOCKDEV_ON_ERROR_AUTO;
     dev->conf.werror = BLOCKDEV_ON_ERROR_AUTO;
 
-    if (!blkconf_apply_backend_options(&dev->conf,
-                                       blk_is_read_only(dev->conf.blk),
-                                       false, errp)) {
+    if (!blkconf_apply_backend_options(&dev->conf, read_only, false, errp)) {
         return;
     }
 
-- 
2.20.1

Re: [Qemu-devel] [PATCH for-4.1 1/2] fdc: Fix inserting read-only media in empty drive

[Max Reitz]

[-- Attachment #1.1: Type: text/plain, Size: 1056 bytes --]

On 30.07.19 16:57, Kevin Wolf wrote:
> In order to insert a read-only medium (i.e. a read-only block node) to
> the BlockBackend of a floppy drive, we must not have taken write
> permissions on that BlockBackend, or the operation will fail with the
> error message "Block node is read-only".
> 
> The device already takes care to remove all permissions when the medium
> is ejected, but the state isn't correct if the drive is initially empty:
> It uses blk_is_read_only() to check whether write permissions should be
> taken, but this function returns false for empty BlockBackends in the
> common case.
> 
> Fix floppy_drive_realize() to avoid taking write permissions if the
> drive is empty.

...and once the drive is loaded with anything, fd_change_cb() calls
blkconf_apply_backend_option() again with the updated RO state.  Looks
correct.

> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  hw/block/fdc.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [Qemu-devel] [PATCH for-4.1 1/2] fdc: Fix inserting read-only media in empty drive

[John Snow]

On 7/30/19 10:57 AM, Kevin Wolf wrote:
> In order to insert a read-only medium (i.e. a read-only block node) to
> the BlockBackend of a floppy drive, we must not have taken write
> permissions on that BlockBackend, or the operation will fail with the
> error message "Block node is read-only".
> 
> The device already takes care to remove all permissions when the medium
> is ejected, but the state isn't correct if the drive is initially empty:
> It uses blk_is_read_only() to check whether write permissions should be
> taken, but this function returns false for empty BlockBackends in the
> common case.
> 
> Fix floppy_drive_realize() to avoid taking write permissions if the
> drive is empty.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  hw/block/fdc.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/block/fdc.c b/hw/block/fdc.c
> index 77af9979de..9b24cb9b85 100644
> --- a/hw/block/fdc.c
> +++ b/hw/block/fdc.c
> @@ -514,6 +514,7 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp)
>      FloppyDrive *dev = FLOPPY_DRIVE(qdev);
>      FloppyBus *bus = FLOPPY_BUS(qdev->parent_bus);
>      FDrive *drive;
> +    bool read_only;
>      int ret;
>  
>      if (dev->unit == -1) {
> @@ -542,6 +543,12 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp)
>          dev->conf.blk = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);
>          ret = blk_attach_dev(dev->conf.blk, qdev);
>          assert(ret == 0);
> +
> +        /* Don't take write permissions on an empty drive to allow attaching a
> +         * read-only node later */
> +        read_only = true;
> +    } else {
> +        read_only = !blk_bs(dev->conf.blk) || blk_is_read_only(dev->conf.blk);
>      }
>  
>      blkconf_blocksizes(&dev->conf);
> @@ -559,9 +566,7 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp)
>      dev->conf.rerror = BLOCKDEV_ON_ERROR_AUTO;
>      dev->conf.werror = BLOCKDEV_ON_ERROR_AUTO;
>  
> -    if (!blkconf_apply_backend_options(&dev->conf,
> -                                       blk_is_read_only(dev->conf.blk),
> -                                       false, errp)) {
> +    if (!blkconf_apply_backend_options(&dev->conf, read_only, false, errp)) {
>          return;
>      }
>  
> 

Smells correct.

Reviewed-by: John Snow <jsnow@redhat.com>

[Qemu-devel] [PATCH for-4.1 2/2] iotests/118: Test inserting a read-only medium

[Kevin Wolf]

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 tests/qemu-iotests/118     | 6 +++++-
 tests/qemu-iotests/118.out | 4 ++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/tests/qemu-iotests/118 b/tests/qemu-iotests/118
index 603e10e8a2..499c5f0901 100755
--- a/tests/qemu-iotests/118
+++ b/tests/qemu-iotests/118
@@ -207,10 +207,11 @@ class GeneralChangeTestsBaseClass(ChangeBaseClass):
             self.assert_qmp(result, 'return[0]/tray_open', False)
         self.assert_qmp(result, 'return[0]/inserted/image/filename', new_img)
 
-    def test_cycle(self):
+    def test_cycle(self, read_only_node=False):
         result = self.vm.qmp('blockdev-add',
                              node_name='new',
                              driver=iotests.imgfmt,
+                             read_only=read_only_node,
                              file={'filename': new_img,
                                     'driver': 'file'})
         self.assert_qmp(result, 'return', {})
@@ -257,6 +258,9 @@ class GeneralChangeTestsBaseClass(ChangeBaseClass):
             self.assert_qmp(result, 'return[0]/tray_open', False)
         self.assert_qmp(result, 'return[0]/inserted/image/filename', new_img)
 
+    def test_cycle_read_only_media(self):
+        self.test_cycle(True)
+
     def test_close_on_closed(self):
         result = self.vm.qmp('blockdev-close-tray', id=self.device_name)
         # Should be a no-op
diff --git a/tests/qemu-iotests/118.out b/tests/qemu-iotests/118.out
index 6a917130b6..4823c113d5 100644
--- a/tests/qemu-iotests/118.out
+++ b/tests/qemu-iotests/118.out
@@ -1,5 +1,5 @@
-...........................................................
+...............................................................
 ----------------------------------------------------------------------
-Ran 59 tests
+Ran 63 tests
 
 OK
-- 
2.20.1

Re: [Qemu-devel] [PATCH for-4.1 2/2] iotests/118: Test inserting a read-only medium

[Max Reitz]

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On 30.07.19 16:57, Kevin Wolf wrote:
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  tests/qemu-iotests/118     | 6 +++++-
>  tests/qemu-iotests/118.out | 4 ++--
>  2 files changed, 7 insertions(+), 3 deletions(-)

Personally, I wouldn’t mind a

    self.assert_qmp(result, 'return[0]/inserted/ro', read_only_node)

at the end of test_cycle(), but oh well:

Reviewed-by: Max Reitz <mreitz@redhat.com>

(We’d also want it in other places, e.g. test_tray_open_change() should
check that it’s always False for floppy disks, and True for CDs.)


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Re: [Qemu-devel] [PATCH for-4.1 2/2] iotests/118: Test inserting a read-only medium

[John Snow]

On 7/30/19 10:57 AM, Kevin Wolf wrote:
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  tests/qemu-iotests/118     | 6 +++++-
>  tests/qemu-iotests/118.out | 4 ++--
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/tests/qemu-iotests/118 b/tests/qemu-iotests/118
> index 603e10e8a2..499c5f0901 100755
> --- a/tests/qemu-iotests/118
> +++ b/tests/qemu-iotests/118
> @@ -207,10 +207,11 @@ class GeneralChangeTestsBaseClass(ChangeBaseClass):
>              self.assert_qmp(result, 'return[0]/tray_open', False)
>          self.assert_qmp(result, 'return[0]/inserted/image/filename', new_img)
>  
> -    def test_cycle(self):
> +    def test_cycle(self, read_only_node=False):
>          result = self.vm.qmp('blockdev-add',
>                               node_name='new',
>                               driver=iotests.imgfmt,
> +                             read_only=read_only_node,
>                               file={'filename': new_img,
>                                      'driver': 'file'})
>          self.assert_qmp(result, 'return', {})
> @@ -257,6 +258,9 @@ class GeneralChangeTestsBaseClass(ChangeBaseClass):
>              self.assert_qmp(result, 'return[0]/tray_open', False)
>          self.assert_qmp(result, 'return[0]/inserted/image/filename', new_img)
>  
> +    def test_cycle_read_only_media(self):
> +        self.test_cycle(True)
> +
>      def test_close_on_closed(self):
>          result = self.vm.qmp('blockdev-close-tray', id=self.device_name)
>          # Should be a no-op
> diff --git a/tests/qemu-iotests/118.out b/tests/qemu-iotests/118.out
> index 6a917130b6..4823c113d5 100644
> --- a/tests/qemu-iotests/118.out
> +++ b/tests/qemu-iotests/118.out
> @@ -1,5 +1,5 @@
> -...........................................................
> +...............................................................
>  ----------------------------------------------------------------------
> -Ran 59 tests
> +Ran 63 tests
>  
>  OK
> 

Reviewed-by: John Snow <jsnow@redhat.com>