[PATCH net] netdev-genl: avoid empty messages in queue dump

[PATCH net] netdev-genl: avoid empty messages in queue dump

[Jakub Kicinski]

Empty netlink responses from do() are not correct (as opposed to
dump() where not dumping anything is perfectly fine).
We should return an error if the target object does not exist,
in this case if the netdev is down it has no queues.

Fixes: 6b6171db7fc8 ("netdev-genl: Add netlink framework functions for queue")
Reported-by: syzbot+0a884bc2d304ce4af70f@syzkaller.appspotmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: jdamato@fastly.com
CC: almasrymina@google.com
CC: sridhar.samudrala@intel.com
CC: amritha.nambiar@intel.com
---
 net/core/netdev-genl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 9527dd46e4dc..b4becd4065d9 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -430,10 +430,10 @@ static int
 netdev_nl_queue_fill(struct sk_buff *rsp, struct net_device *netdev, u32 q_idx,
 		     u32 q_type, const struct genl_info *info)
 {
-	int err = 0;
+	int err;
 
 	if (!(netdev->flags & IFF_UP))
-		return err;
+		return -ENOENT;
 
 	err = netdev_nl_queue_validate(netdev, q_idx, q_type);
 	if (err)
-- 
2.47.1

Re: [PATCH net] netdev-genl: avoid empty messages in queue dump

[Jakub Kicinski]

On Tue, 17 Dec 2024 18:25:08 -0800 Jakub Kicinski wrote:
> Subject: [PATCH net] netdev-genl: avoid empty messages in queue dump
> 
> Empty netlink responses from do() are not correct (as opposed to
> dump() where not dumping anything is perfectly fine).

Well.. I shouldn't have said "dump" in the subject, then.
Let's see how the review goes, I can adjust when applying.

Re: [PATCH net] netdev-genl: avoid empty messages in queue dump

[Eric Dumazet]

On Wed, Dec 18, 2024 at 3:25 AM Jakub Kicinski <kuba@kernel.org> wrote:
>
> Empty netlink responses from do() are not correct (as opposed to
> dump() where not dumping anything is perfectly fine).
> We should return an error if the target object does not exist,
> in this case if the netdev is down it has no queues.
>
> Fixes: 6b6171db7fc8 ("netdev-genl: Add netlink framework functions for queue")
> Reported-by: syzbot+0a884bc2d304ce4af70f@syzkaller.appspotmail.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net] netdev-genl: avoid empty messages in queue dump

[Joe Damato]

On Tue, Dec 17, 2024 at 06:25:08PM -0800, Jakub Kicinski wrote:
> Empty netlink responses from do() are not correct (as opposed to
> dump() where not dumping anything is perfectly fine).
> We should return an error if the target object does not exist,
> in this case if the netdev is down it has no queues.
> 
> Fixes: 6b6171db7fc8 ("netdev-genl: Add netlink framework functions for queue")
> Reported-by: syzbot+0a884bc2d304ce4af70f@syzkaller.appspotmail.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> CC: jdamato@fastly.com
> CC: almasrymina@google.com
> CC: sridhar.samudrala@intel.com
> CC: amritha.nambiar@intel.com
> ---
>  net/core/netdev-genl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
> index 9527dd46e4dc..b4becd4065d9 100644
> --- a/net/core/netdev-genl.c
> +++ b/net/core/netdev-genl.c
> @@ -430,10 +430,10 @@ static int
>  netdev_nl_queue_fill(struct sk_buff *rsp, struct net_device *netdev, u32 q_idx,
>  		     u32 q_type, const struct genl_info *info)
>  {
> -	int err = 0;
> +	int err;
>  
>  	if (!(netdev->flags & IFF_UP))
> -		return err;
> +		return -ENOENT;
>  
>  	err = netdev_nl_queue_validate(netdev, q_idx, q_type);
>  	if (err)

Reviewed-by: Joe Damato <jdamato@fastly.com>

Re: [PATCH net] netdev-genl: avoid empty messages in queue dump

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 17 Dec 2024 18:25:08 -0800 you wrote:
> Empty netlink responses from do() are not correct (as opposed to
> dump() where not dumping anything is perfectly fine).
> We should return an error if the target object does not exist,
> in this case if the netdev is down it has no queues.
> 
> Fixes: 6b6171db7fc8 ("netdev-genl: Add netlink framework functions for queue")
> Reported-by: syzbot+0a884bc2d304ce4af70f@syzkaller.appspotmail.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> 
> [...]

Here is the summary with links:
  - [net] netdev-genl: avoid empty messages in queue dump
    https://git.kernel.org/netdev/net/c/5eb70dbebf32

You are awesome, thank you!
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