[Xen PATCH] xen-netback: fix error handling output

[Xen PATCH] xen-netback: fix error handling output

[Arnd Bergmann]

The connect function prints an unintialized error code after an
earlier initialization was removed:

drivers/net/xen-netback/xenbus.c: In function 'connect':
drivers/net/xen-netback/xenbus.c:938:3: error: 'err' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This prints it as -EINVAL instead, which seems to be the most
appropriate error code. Before the patch that caused the warning,
this would print a positive number returned by vsscanf() instead,
which is also wrong. We probably don't need a backport though,
as fixing the warning here should be sufficient.

Fixes: f95842e7a9f2 ("xen: make use of xenbus_read_unsigned() in xen-netback")
Fixes: 8d3d53b3e433 ("xen-netback: Add support for multiple queues")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/xen-netback/xenbus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 7356e00fac54..bfed79877b8a 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -935,7 +935,7 @@ static void connect(struct backend_info *be)
 					"multi-queue-num-queues", 1);
 	if (requested_num_queues > xenvif_max_queues) {
 		/* buggy or malicious guest */
-		xenbus_dev_fatal(dev, err,
+		xenbus_dev_fatal(dev, -EINVAL,
 				 "guest requested %u queues, exceeding the maximum of %u.",
 				 requested_num_queues, xenvif_max_queues);
 		return;
-- 
2.9.0

RE: [Xen PATCH] xen-netback: fix error handling output

[Paul Durrant]

> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@arndb.de]
> Sent: 08 November 2016 13:35
> To: David Vrabel <david.vrabel@citrix.com>
> Cc: Arnd Bergmann <arnd@arndb.de>; Wei Liu <wei.liu2@citrix.com>; Paul
> Durrant <Paul.Durrant@citrix.com>; David S. Miller
> <davem@davemloft.net>; Juergen Gross <jgross@suse.com>; Filipe Manco
> <filipe.manco@neclab.eu>; xen-devel@lists.xenproject.org;
> netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: [Xen PATCH] xen-netback: fix error handling output
> 
> The connect function prints an unintialized error code after an
> earlier initialization was removed:
> 
> drivers/net/xen-netback/xenbus.c: In function 'connect':
> drivers/net/xen-netback/xenbus.c:938:3: error: 'err' may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
> 
> This prints it as -EINVAL instead, which seems to be the most
> appropriate error code. Before the patch that caused the warning,
> this would print a positive number returned by vsscanf() instead,
> which is also wrong. We probably don't need a backport though,
> as fixing the warning here should be sufficient.
> 
> Fixes: f95842e7a9f2 ("xen: make use of xenbus_read_unsigned() in xen-
> netback")
> Fixes: 8d3d53b3e433 ("xen-netback: Add support for multiple queues")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Yes, I'd say EINVAL was most appropriate.

Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

> ---
>  drivers/net/xen-netback/xenbus.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-
> netback/xenbus.c
> index 7356e00fac54..bfed79877b8a 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -935,7 +935,7 @@ static void connect(struct backend_info *be)
>  					"multi-queue-num-queues", 1);
>  	if (requested_num_queues > xenvif_max_queues) {
>  		/* buggy or malicious guest */
> -		xenbus_dev_fatal(dev, err,
> +		xenbus_dev_fatal(dev, -EINVAL,
>  				 "guest requested %u queues, exceeding the
> maximum of %u.",
>  				 requested_num_queues,
> xenvif_max_queues);
>  		return;
> --
> 2.9.0

Re: [Xen PATCH] xen-netback: fix error handling output

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Tue,  8 Nov 2016 14:34:34 +0100

> The connect function prints an unintialized error code after an
> earlier initialization was removed:
> 
> drivers/net/xen-netback/xenbus.c: In function 'connect':
> drivers/net/xen-netback/xenbus.c:938:3: error: 'err' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 
> This prints it as -EINVAL instead, which seems to be the most
> appropriate error code. Before the patch that caused the warning,
> this would print a positive number returned by vsscanf() instead,
> which is also wrong. We probably don't need a backport though,
> as fixing the warning here should be sufficient.
> 
> Fixes: f95842e7a9f2 ("xen: make use of xenbus_read_unsigned() in xen-netback")
> Fixes: 8d3d53b3e433 ("xen-netback: Add support for multiple queues")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

That first Fixes: commit mentioned is in neither of my trees, so I
assume it is in the Xen tree and thus this fix should get applied
there.

Re: [Xen PATCH] xen-netback: fix error handling output

[Juergen Gross]

On 08/11/16 14:34, Arnd Bergmann wrote:
> The connect function prints an unintialized error code after an
> earlier initialization was removed:
> 
> drivers/net/xen-netback/xenbus.c: In function 'connect':
> drivers/net/xen-netback/xenbus.c:938:3: error: 'err' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 
> This prints it as -EINVAL instead, which seems to be the most
> appropriate error code. Before the patch that caused the warning,
> this would print a positive number returned by vsscanf() instead,
> which is also wrong. We probably don't need a backport though,
> as fixing the warning here should be sufficient.
> 
> Fixes: f95842e7a9f2 ("xen: make use of xenbus_read_unsigned() in xen-netback")
> Fixes: 8d3d53b3e433 ("xen-netback: Add support for multiple queues")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Applied to xen/tip.git for-linus-4.10


Thanks,

Juergen

> ---
>  drivers/net/xen-netback/xenbus.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
> index 7356e00fac54..bfed79877b8a 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -935,7 +935,7 @@ static void connect(struct backend_info *be)
>  					"multi-queue-num-queues", 1);
>  	if (requested_num_queues > xenvif_max_queues) {
>  		/* buggy or malicious guest */
> -		xenbus_dev_fatal(dev, err,
> +		xenbus_dev_fatal(dev, -EINVAL,
>  				 "guest requested %u queues, exceeding the maximum of %u.",
>  				 requested_num_queues, xenvif_max_queues);
>  		return;
>