Patchwork [3.5.y.z,extended,stable] Patch "virtio: Don't access index after unregister." has been added to staging queue

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Submitter Herton Ronaldo Krzesinski
Date Dec. 6, 2012, 3:24 a.m.
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Permalink /patch/204120/
State New
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Herton Ronaldo Krzesinski - Dec. 6, 2012, 3:24 a.m.
This is a note to let you know that I have just added a patch titled

    virtio: Don't access index after unregister.

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



From 41d829cae4178db309f88020b877a144d39d2f0c Mon Sep 17 00:00:00 2001
From: Cornelia Huck <>
Date: Fri, 9 Nov 2012 14:54:12 +1030
Subject: [PATCH] virtio: Don't access index after unregister.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-Extended-Stable: 3.5

commit 237242bddc99041e15a4ca51b8439657cadaff17 upstream.

Virtio wants to release used indices after the corresponding
virtio device has been unregistered. However, virtio does not
hold an extra reference, giving up its last reference with
device_unregister(), making accessing dev->index afterwards

I actually saw problems when testing my (not-yet-merged)
virtio-ccw code:

- device_add virtio-net,id=xxx
-> creates device virtio<n> with n>0

- device_del xxx
-> deletes virtio<n>, but calls ida_simple_remove with an
   index of 0

- device_add virtio-net,id=xxx
-> tries to add virtio0, which is still in use...

So let's save the index we want to release before calling

Signed-off-by: Cornelia Huck <>
Acked-by: Sjur Brændeland <>
Signed-off-by: Rusty Russell <>
Signed-off-by: Herton Ronaldo Krzesinski <>
 drivers/virtio/virtio.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)



diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index f355807..acc77a2 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -222,8 +222,10 @@  EXPORT_SYMBOL_GPL(register_virtio_device);

 void unregister_virtio_device(struct virtio_device *dev)
+	int index = dev->index; /* save for after device release */
-	ida_simple_remove(&virtio_index_ida, dev->index);
+	ida_simple_remove(&virtio_index_ida, index);