[PATCH net-next] net: print error if SO_BUSY_POLL_BUDGET is large

[PATCH net-next] net: print error if SO_BUSY_POLL_BUDGET is large

[Joe Damato]

When drivers call netif_napi_add_weight with a weight that is larger
than NAPI_POLL_WEIGHT, the networking code allows the larger weight, but
prints an error.

Replicate this check for SO_BUSY_POLL_BUDGET; check if the user
specified amount exceeds NAPI_POLL_WEIGHT, allow it anyway, but print an
error.

Signed-off-by: Joe Damato <jdamato@fastly.com>
---
 net/core/sock.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/sock.c b/net/core/sock.c
index 158dbdebce6a..ed243bd0dd77 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1153,6 +1153,9 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
 			return -EPERM;
 		if (val < 0 || val > U16_MAX)
 			return -EINVAL;
+		if (val > NAPI_POLL_WEIGHT)
+			pr_err("SO_BUSY_POLL_BUDGET %u exceeds suggested maximum %u\n", val,
+			       NAPI_POLL_WEIGHT);
 		WRITE_ONCE(sk->sk_busy_poll_budget, val);
 		return 0;
 #endif
-- 
2.25.1

Re: [PATCH net-next] net: print error if SO_BUSY_POLL_BUDGET is large

[Eric Dumazet]

On Thu, Jan 25, 2024 at 8:18 PM Joe Damato <jdamato@fastly.com> wrote:
>
> When drivers call netif_napi_add_weight with a weight that is larger
> than NAPI_POLL_WEIGHT, the networking code allows the larger weight, but
> prints an error.
>
> Replicate this check for SO_BUSY_POLL_BUDGET; check if the user
> specified amount exceeds NAPI_POLL_WEIGHT, allow it anyway, but print an
> error.
>
> Signed-off-by: Joe Damato <jdamato@fastly.com>
> ---
>  net/core/sock.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 158dbdebce6a..ed243bd0dd77 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1153,6 +1153,9 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
>                         return -EPERM;
>                 if (val < 0 || val > U16_MAX)
>                         return -EINVAL;
> +               if (val > NAPI_POLL_WEIGHT)
> +                       pr_err("SO_BUSY_POLL_BUDGET %u exceeds suggested maximum %u\n", val,
> +                              NAPI_POLL_WEIGHT);
>                 WRITE_ONCE(sk->sk_busy_poll_budget, val);
>                 return 0;

This is code run by privileged (CAP_NET_ADMIN) users,
please do not spam the console with such a message.

My point was : Do not allow an unpriv user to set an arbitrary value.

netif_napi_add_weight() is used from kernel drivers, we network
maintainers usually object
if a driver attempts to use a big value, at code review time.

Re: [PATCH net-next] net: print error if SO_BUSY_POLL_BUDGET is large

[Breno Leitao]

Hi Joe,

On Thu, Jan 25, 2024 at 07:18:40PM +0000, Joe Damato wrote:
> When drivers call netif_napi_add_weight with a weight that is larger
> than NAPI_POLL_WEIGHT, the networking code allows the larger weight, but
> prints an error.
> 
> Replicate this check for SO_BUSY_POLL_BUDGET; check if the user
> specified amount exceeds NAPI_POLL_WEIGHT, allow it anyway, but print an
> error.
> 
> Signed-off-by: Joe Damato <jdamato@fastly.com>
> ---
>  net/core/sock.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 158dbdebce6a..ed243bd0dd77 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1153,6 +1153,9 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
>  			return -EPERM;
>  		if (val < 0 || val > U16_MAX)
>  			return -EINVAL;
> +		if (val > NAPI_POLL_WEIGHT)
> +			pr_err("SO_BUSY_POLL_BUDGET %u exceeds suggested maximum %u\n", val,
> +			       NAPI_POLL_WEIGHT);

'val' is a signed value variable. I suspect it will never be negative given
the line above (val < 0 || val > U16_MAX), but, I am wondering if you
should still print it as signed integer (%d) to keep it consistent.