[ 3.5.y.z extended stable ] Patch "xen-netback: correctly return errors from" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Thu Feb 28 11:59:24 UTC 2013

This is a note to let you know that I have just added a patch titled

    xen-netback: correctly return errors from

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


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 1022bcc03a236fd5537386ac8c2a864200d59f5e Mon Sep 17 00:00:00 2001
From: David Vrabel <david.vrabel at citrix.com>
Date: Thu, 14 Feb 2013 03:18:57 +0000
Subject: [PATCH] xen-netback: correctly return errors from

commit 35876b5ffc154c357476b2c3bdab10feaf4bd8f0 upstream.

netbk_count_requests() could detect an error, call
netbk_fatal_tx_error() but return 0.  The vif may then be used
afterwards (e.g., in a call to netbk_tx_error().

Since netbk_fatal_tx_error() could set vif->refcnt to 1, the vif may
be freed immediately after the call to netbk_fatal_tx_error() (e.g.,
if the vif is also removed).

Netback thread              Xenwatch thread
netbk_fatal_tx_err()        netback_remove()
netbk_tx_err() Oops!

Signed-off-by: Wei Liu <wei.liu2 at citrix.com>
Signed-off-by: Jan Beulich <JBeulich at suse.com>
Signed-off-by: David Vrabel <david.vrabel at citrix.com>
Reported-by: Christopher S. Aker <caker at theshore.net>
Acked-by: Ian Campbell <ian.campbell at citrix.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 drivers/net/xen-netback/netback.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index f3c3a68..a98f012 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -882,13 +882,13 @@ static int netbk_count_requests(struct xenvif *vif,
 		if (frags >= work_to_do) {
 			netdev_err(vif->dev, "Need more frags\n");
-			return -frags;
+			return -ENODATA;

 		if (unlikely(frags >= MAX_SKB_FRAGS)) {
 			netdev_err(vif->dev, "Too many frags\n");
-			return -frags;
+			return -E2BIG;

 		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
@@ -896,7 +896,7 @@ static int netbk_count_requests(struct xenvif *vif,
 		if (txp->size > first->size) {
 			netdev_err(vif->dev, "Frag is bigger than frame.\n");
-			return -frags;
+			return -EIO;

 		first->size -= txp->size;
@@ -906,7 +906,7 @@ static int netbk_count_requests(struct xenvif *vif,
 			netdev_err(vif->dev, "txp->offset: %x, size: %u\n",
 				 txp->offset, txp->size);
-			return -frags;
+			return -EINVAL;
 	} while ((txp++)->flags & XEN_NETTXF_more_data);
 	return frags;

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