Patchwork [1/2] xen-netback: correctly return errors from netbk_count_requests()

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Submitter David Vrabel
Date Feb. 14, 2013, 1:18 p.m.
Message ID <1360847938-11185-2-git-send-email-david.vrabel@citrix.com>
Download mbox | patch
Permalink /patch/220442/
State Accepted
Delegated to: David Miller
Headers show

Comments

David Vrabel - Feb. 14, 2013, 1:18 p.m.
From: David Vrabel <david.vrabel@citrix.com>

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()
                              xenvif_disconnect()
                                ...
                                free_netdev()
netbk_tx_err() Oops!

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 drivers/net/xen-netback/netback.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
Ian Campbell - Feb. 14, 2013, 4:39 p.m.
On Thu, 2013-02-14 at 13:18 +0000, David Vrabel wrote:
> From: David Vrabel <david.vrabel@citrix.com>
> 
> 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()
>                               xenvif_disconnect()
>                                 ...
>                                 free_netdev()
> netbk_tx_err() Oops!
> 
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> Signed-off-by: Jan Beulich <JBeulich@suse.com>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>

Reported-by: Christopher S. Aker <caker@theshore.net>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

Although I would like to add a Tested-by: Christopher too if possible.

David (M) this should go to stable please.

> ---
>  drivers/net/xen-netback/netback.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 2b9520c..cd49ba9 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -911,13 +911,13 @@ static int netbk_count_requests(struct xenvif *vif,
>  		if (frags >= work_to_do) {
>  			netdev_err(vif->dev, "Need more frags\n");
>  			netbk_fatal_tx_err(vif);
> -			return -frags;
> +			return -ENODATA;
>  		}
>  
>  		if (unlikely(frags >= MAX_SKB_FRAGS)) {
>  			netdev_err(vif->dev, "Too many frags\n");
>  			netbk_fatal_tx_err(vif);
> -			return -frags;
> +			return -E2BIG;
>  		}
>  
>  		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
> @@ -925,7 +925,7 @@ static int netbk_count_requests(struct xenvif *vif,
>  		if (txp->size > first->size) {
>  			netdev_err(vif->dev, "Frag is bigger than frame.\n");
>  			netbk_fatal_tx_err(vif);
> -			return -frags;
> +			return -EIO;
>  		}
>  
>  		first->size -= txp->size;
> @@ -935,7 +935,7 @@ static int netbk_count_requests(struct xenvif *vif,
>  			netdev_err(vif->dev, "txp->offset: %x, size: %u\n",
>  				 txp->offset, txp->size);
>  			netbk_fatal_tx_err(vif);
> -			return -frags;
> +			return -EINVAL;
>  		}
>  	} while ((txp++)->flags & XEN_NETTXF_more_data);
>  	return frags;


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Patch

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 2b9520c..cd49ba9 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -911,13 +911,13 @@  static int netbk_count_requests(struct xenvif *vif,
 		if (frags >= work_to_do) {
 			netdev_err(vif->dev, "Need more frags\n");
 			netbk_fatal_tx_err(vif);
-			return -frags;
+			return -ENODATA;
 		}
 
 		if (unlikely(frags >= MAX_SKB_FRAGS)) {
 			netdev_err(vif->dev, "Too many frags\n");
 			netbk_fatal_tx_err(vif);
-			return -frags;
+			return -E2BIG;
 		}
 
 		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
@@ -925,7 +925,7 @@  static int netbk_count_requests(struct xenvif *vif,
 		if (txp->size > first->size) {
 			netdev_err(vif->dev, "Frag is bigger than frame.\n");
 			netbk_fatal_tx_err(vif);
-			return -frags;
+			return -EIO;
 		}
 
 		first->size -= txp->size;
@@ -935,7 +935,7 @@  static int netbk_count_requests(struct xenvif *vif,
 			netdev_err(vif->dev, "txp->offset: %x, size: %u\n",
 				 txp->offset, txp->size);
 			netbk_fatal_tx_err(vif);
-			return -frags;
+			return -EINVAL;
 		}
 	} while ((txp++)->flags & XEN_NETTXF_more_data);
 	return frags;