[PATCH net v2] tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS

[PATCH net v2] tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS

[wangyunjian]

From: Yunjian Wang <wangyunjian@huawei.com>

Currently the tun_napi_alloc_frags() function returns -ENOMEM when the
number of iovs exceeds MAX_SKB_FRAGS + 1. However this is inappropriate,
we should use -EMSGSIZE instead of -ENOMEM.

The following distinctions are matters:
1. the caller need to drop the bad packet when -EMSGSIZE is returned,
   which means meeting a persistent failure.
2. the caller can try again when -ENOMEM is returned, which means
   meeting a transient failure.

Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Acked-by: Willem de Bruijn <willemb@google.com>
---
v2:
  * update commit log suggested by Willem de Bruijn
---
 drivers/net/tun.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2dc1988a8973..15c6dd7fb04c 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1365,7 +1365,7 @@ static struct sk_buff *tun_napi_alloc_frags(struct tun_file *tfile,
 	int i;
 
 	if (it->nr_segs > MAX_SKB_FRAGS + 1)
-		return ERR_PTR(-ENOMEM);
+		return ERR_PTR(-EMSGSIZE);
 
 	local_bh_disable();
 	skb = napi_get_frags(&tfile->napi);
-- 
2.23.0

Re: [PATCH net v2] tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS

[Jason Wang]

On 2020/12/25 上午10:52, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@huawei.com>
>
> Currently the tun_napi_alloc_frags() function returns -ENOMEM when the
> number of iovs exceeds MAX_SKB_FRAGS + 1. However this is inappropriate,
> we should use -EMSGSIZE instead of -ENOMEM.
>
> The following distinctions are matters:
> 1. the caller need to drop the bad packet when -EMSGSIZE is returned,
>     which means meeting a persistent failure.
> 2. the caller can try again when -ENOMEM is returned, which means
>     meeting a transient failure.
>
> Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> Acked-by: Willem de Bruijn <willemb@google.com>
> ---
> v2:
>    * update commit log suggested by Willem de Bruijn
> ---
>   drivers/net/tun.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 2dc1988a8973..15c6dd7fb04c 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1365,7 +1365,7 @@ static struct sk_buff *tun_napi_alloc_frags(struct tun_file *tfile,
>   	int i;
>   
>   	if (it->nr_segs > MAX_SKB_FRAGS + 1)
> -		return ERR_PTR(-ENOMEM);
> +		return ERR_PTR(-EMSGSIZE);
>   
>   	local_bh_disable();
>   	skb = napi_get_frags(&tfile->napi);


Acked-by: Jason Wang <jasowang@redhat.com>

Re: [PATCH net v2] tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS

[Michael S. Tsirkin]

On Fri, Dec 25, 2020 at 10:52:16AM +0800, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@huawei.com>
> 
> Currently the tun_napi_alloc_frags() function returns -ENOMEM when the
> number of iovs exceeds MAX_SKB_FRAGS + 1. However this is inappropriate,
> we should use -EMSGSIZE instead of -ENOMEM.
> 
> The following distinctions are matters:
> 1. the caller need to drop the bad packet when -EMSGSIZE is returned,
>    which means meeting a persistent failure.
> 2. the caller can try again when -ENOMEM is returned, which means
>    meeting a transient failure.
> 
> Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> Acked-by: Willem de Bruijn <willemb@google.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> v2:
>   * update commit log suggested by Willem de Bruijn
> ---
>  drivers/net/tun.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 2dc1988a8973..15c6dd7fb04c 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1365,7 +1365,7 @@ static struct sk_buff *tun_napi_alloc_frags(struct tun_file *tfile,
>  	int i;
>  
>  	if (it->nr_segs > MAX_SKB_FRAGS + 1)
> -		return ERR_PTR(-ENOMEM);
> +		return ERR_PTR(-EMSGSIZE);
>  
>  	local_bh_disable();
>  	skb = napi_get_frags(&tfile->napi);
> -- 
> 2.23.0

Re: [PATCH net v2] tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS

[Jakub Kicinski]

On Fri, 25 Dec 2020 10:52:16 +0800 wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@huawei.com>
> 
> Currently the tun_napi_alloc_frags() function returns -ENOMEM when the
> number of iovs exceeds MAX_SKB_FRAGS + 1. However this is inappropriate,
> we should use -EMSGSIZE instead of -ENOMEM.
> 
> The following distinctions are matters:
> 1. the caller need to drop the bad packet when -EMSGSIZE is returned,
>    which means meeting a persistent failure.
> 2. the caller can try again when -ENOMEM is returned, which means
>    meeting a transient failure.
> 
> Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> Acked-by: Willem de Bruijn <willemb@google.com>

Applied, thanks everyone!