[dpdk-dev] [PATCH] ethdev: avoid usage of uninit device info in bad port case

[dpdk-dev] [PATCH] ethdev: avoid usage of uninit device info in bad port case

[Andrew Rybchenko]

rte_eth_dev_info_get() returns void and caller does know if the function
does its job or not. Changing of the return value to int would be
API/ABI breakage which requires deprecation process and cannot be
backported to stable branches. For now, make sure that device info is
initialized even in the case of invalid port ID.

Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
Cc: stable@dpdk.org

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
---
 lib/librte_ethdev/rte_ethdev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
index 64191737c..97b093edc 100644
--- a/lib/librte_ethdev/rte_ethdev.c
+++ b/lib/librte_ethdev/rte_ethdev.c
@@ -2552,10 +2552,11 @@ rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info *dev_info)
 		.nb_mtu_seg_max = UINT16_MAX,
 	};
 
+	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
+
 	RTE_ETH_VALID_PORTID_OR_RET(port_id);
 	dev = &rte_eth_devices[port_id];
 
-	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
 	dev_info->rx_desc_lim = lim;
 	dev_info->tx_desc_lim = lim;
 	dev_info->device = dev->device;
-- 
2.17.1

Re: [dpdk-dev] [PATCH] ethdev: avoid usage of uninit device info in bad port case

[Ferruh Yigit]

On 7/23/2019 10:13 AM, Andrew Rybchenko wrote:
> rte_eth_dev_info_get() returns void and caller does know if the function
> does its job or not. Changing of the return value to int would be
> API/ABI breakage which requires deprecation process and cannot be
> backported to stable branches. For now, make sure that device info is
> initialized even in the case of invalid port ID.

+1 to return a status from function for long term.

But someone looks below code can think we are doing an unnecessary memset for
the error case, and will fix it :)
What do you think adding a comment to prevent this?

> 
> Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
> ---
>  lib/librte_ethdev/rte_ethdev.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
> index 64191737c..97b093edc 100644
> --- a/lib/librte_ethdev/rte_ethdev.c
> +++ b/lib/librte_ethdev/rte_ethdev.c
> @@ -2552,10 +2552,11 @@ rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info *dev_info)
>  		.nb_mtu_seg_max = UINT16_MAX,
>  	};
>  
> +	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
> +
>  	RTE_ETH_VALID_PORTID_OR_RET(port_id);
>  	dev = &rte_eth_devices[port_id];
>  
> -	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
>  	dev_info->rx_desc_lim = lim;
>  	dev_info->tx_desc_lim = lim;
>  	dev_info->device = dev->device;
> 

Re: [dpdk-dev] [PATCH] ethdev: avoid usage of uninit device info in bad port case

[Andrew Rybchenko]

On 7/23/19 1:40 PM, Ferruh Yigit wrote:
> On 7/23/2019 10:13 AM, Andrew Rybchenko wrote:
>> rte_eth_dev_info_get() returns void and caller does know if the function
>> does its job or not. Changing of the return value to int would be
>> API/ABI breakage which requires deprecation process and cannot be
>> backported to stable branches. For now, make sure that device info is
>> initialized even in the case of invalid port ID.
> +1 to return a status from function for long term.

Thomas, what do you think? Should we finally fix it?
I think it is almost harmless API/ABI breakage.
If yes, I'll send deprecation notice to do it in v19.11.

> But someone looks below code can think we are doing an unnecessary memset for
> the error case, and will fix it :)
> What do you think adding a comment to prevent this?

See v2.

Re: [dpdk-dev] [PATCH] ethdev: avoid usage of uninit device info in bad port case

[Thomas Monjalon]

23/07/2019 14:16, Andrew Rybchenko:
> On 7/23/19 1:40 PM, Ferruh Yigit wrote:
> > On 7/23/2019 10:13 AM, Andrew Rybchenko wrote:
> >> rte_eth_dev_info_get() returns void and caller does know if the function
> >> does its job or not. Changing of the return value to int would be
> >> API/ABI breakage which requires deprecation process and cannot be
> >> backported to stable branches. For now, make sure that device info is
> >> initialized even in the case of invalid port ID.
> > +1 to return a status from function for long term.
> 
> Thomas, what do you think? Should we finally fix it?
> I think it is almost harmless API/ABI breakage.
> If yes, I'll send deprecation notice to do it in v19.11.

Yes, generally speaking we should not have any void return in API.

[dpdk-dev] [PATCH v2] ethdev: avoid usage of uninit device info in bad port case

[Andrew Rybchenko]

rte_eth_dev_info_get() returns void and caller does know if the function
does its job or not. Changing of the return value to int would be
API/ABI breakage which requires deprecation process and cannot be
backported to stable branches. For now, make sure that device info is
initialized even in the case of invalid port ID.

Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
Cc: stable@dpdk.org

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
---
 lib/librte_ethdev/rte_ethdev.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
index 64191737c..17d183e1f 100644
--- a/lib/librte_ethdev/rte_ethdev.c
+++ b/lib/librte_ethdev/rte_ethdev.c
@@ -2552,10 +2552,15 @@ rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info *dev_info)
 		.nb_mtu_seg_max = UINT16_MAX,
 	};
 
+	/*
+	 * Init dev_info before port_id check since caller does not have
+	 * return status and does not know if get is successful or not.
+	 */
+	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
+
 	RTE_ETH_VALID_PORTID_OR_RET(port_id);
 	dev = &rte_eth_devices[port_id];
 
-	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
 	dev_info->rx_desc_lim = lim;
 	dev_info->tx_desc_lim = lim;
 	dev_info->device = dev->device;
-- 
2.17.1

Re: [dpdk-dev] [PATCH v2] ethdev: avoid usage of uninit device info in bad port case

[Thomas Monjalon]

23/07/2019 14:11, Andrew Rybchenko:
> rte_eth_dev_info_get() returns void and caller does know if the function
> does its job or not. Changing of the return value to int would be
> API/ABI breakage which requires deprecation process and cannot be
> backported to stable branches. For now, make sure that device info is
> initialized even in the case of invalid port ID.
> 
> Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
> ---
> --- a/lib/librte_ethdev/rte_ethdev.c
> +++ b/lib/librte_ethdev/rte_ethdev.c
> +	/*
> +	 * Init dev_info before port_id check since caller does not have
> +	 * return status and does not know if get is successful or not.
> +	 */
> +	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));

If someone was using a canary to detect failure, it will be resetted.
Why is it urgent to have this workaround?
Can we wait one more release for the definitive fix with error code?

> +
>  	RTE_ETH_VALID_PORTID_OR_RET(port_id);
>  	dev = &rte_eth_devices[port_id];
>  
> -	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
>  	dev_info->rx_desc_lim = lim;
>  	dev_info->tx_desc_lim = lim;
>  	dev_info->device = dev->device;

Re: [dpdk-dev] [PATCH v2] ethdev: avoid usage of uninit device info in bad port case

[Andrew Rybchenko]

On 7/23/19 4:14 PM, Thomas Monjalon wrote:
> 23/07/2019 14:11, Andrew Rybchenko:
>> rte_eth_dev_info_get() returns void and caller does know if the function
>> does its job or not. Changing of the return value to int would be
>> API/ABI breakage which requires deprecation process and cannot be
>> backported to stable branches. For now, make sure that device info is
>> initialized even in the case of invalid port ID.
>>
>> Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
>> ---
>> --- a/lib/librte_ethdev/rte_ethdev.c
>> +++ b/lib/librte_ethdev/rte_ethdev.c
>> +	/*
>> +	 * Init dev_info before port_id check since caller does not have
>> +	 * return status and does not know if get is successful or not.
>> +	 */
>> +	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
> If someone was using a canary to detect failure, it will be resetted.

I've not thought about such ways to check. I would expected check
for not NULL device or driver_name. It is not defined behaviour of
the function to not touch dev_info in the case of bad port ID.

> Why is it urgent to have this workaround?

Nothing really urgent, but I still think that it is a right fix to be
applied and backported to stable branches.
I really met calls with invalid port ID and it took some time
to understand where uninitialized data come from.

> Can we wait one more release for the definitive fix with error code?

No strong opinion, but definitive fix will not be backported.

>> +
>>   	RTE_ETH_VALID_PORTID_OR_RET(port_id);
>>   	dev = &rte_eth_devices[port_id];
>>   
>> -	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
>>   	dev_info->rx_desc_lim = lim;
>>   	dev_info->tx_desc_lim = lim;
>>   	dev_info->device = dev->device;
>>

Re: [dpdk-dev] [PATCH v2] ethdev: avoid usage of uninit device info in bad port case

[Thomas Monjalon]

23/07/2019 15:34, Andrew Rybchenko:
> On 7/23/19 4:14 PM, Thomas Monjalon wrote:
> > 23/07/2019 14:11, Andrew Rybchenko:
> >> rte_eth_dev_info_get() returns void and caller does know if the function
> >> does its job or not. Changing of the return value to int would be
> >> API/ABI breakage which requires deprecation process and cannot be
> >> backported to stable branches. For now, make sure that device info is
> >> initialized even in the case of invalid port ID.
> >>
> >> Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
> >> Cc: stable@dpdk.org
> >>
> >> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
> >> ---
> >> --- a/lib/librte_ethdev/rte_ethdev.c
> >> +++ b/lib/librte_ethdev/rte_ethdev.c
> >> +	/*
> >> +	 * Init dev_info before port_id check since caller does not have
> >> +	 * return status and does not know if get is successful or not.
> >> +	 */
> >> +	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
> > If someone was using a canary to detect failure, it will be resetted.
> 
> I've not thought about such ways to check. I would expected check
> for not NULL device or driver_name. It is not defined behaviour of
> the function to not touch dev_info in the case of bad port ID.
> 
> > Why is it urgent to have this workaround?
> 
> Nothing really urgent, but I still think that it is a right fix to be
> applied and backported to stable branches.
> I really met calls with invalid port ID and it took some time
> to understand where uninitialized data come from.
> 
> > Can we wait one more release for the definitive fix with error code?
> 
> No strong opinion, but definitive fix will not be backported.

You're right.
Acked-by: Thomas Monjalon <thomas@monjalon.net>

Re: [dpdk-dev] [PATCH v2] ethdev: avoid usage of uninit device info in bad port case

[Thomas Monjalon]

23/07/2019 15:39, Thomas Monjalon:
> 23/07/2019 15:34, Andrew Rybchenko:
> > On 7/23/19 4:14 PM, Thomas Monjalon wrote:
> > > 23/07/2019 14:11, Andrew Rybchenko:
> > >> rte_eth_dev_info_get() returns void and caller does know if the function
> > >> does its job or not. Changing of the return value to int would be
> > >> API/ABI breakage which requires deprecation process and cannot be
> > >> backported to stable branches. For now, make sure that device info is
> > >> initialized even in the case of invalid port ID.
> > >>
> > >> Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
> > >> Cc: stable@dpdk.org
> > >>
> > >> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
> 
> Acked-by: Thomas Monjalon <thomas@monjalon.net>

Applied, thanks