Subject: Re: [PATCH] Revert "net: fix cpu_max_bits_warn() usage in netif_attrmask_next{,_and}"

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 19 Oct 2022 07:49:35 -0400

On Sun, Oct 16, 2022 at 08:09:47PM -0700, Yury Norov wrote:
> This reverts commit 854701ba4c39afae2362ba19a580c461cb183e4f.
> 
> The reverted commit makes netif_attr_test_online() network subsystems
> generating warnings, and it breaks syzkaller testing.
> 
> https://syzkaller.appspot.com/bug?extid=9abe5ecc348676215427
> 
> Signed-off-by: Yury Norov <[email-masked]>

Fixes: 854701ba4c39 ("net: fix cpu_max_bits_warn() usage in netif_attrmask_next{,_and}")
Acked-by: Michael S. Tsirkin <[email-masked]>

> ---
>  include/linux/netdevice.h | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index a36edb0ec199..eddf8ee270e7 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3663,8 +3663,9 @@ static inline bool netif_attr_test_online(unsigned long j,
>  static inline unsigned int netif_attrmask_next(int n, const unsigned long *srcp,
>  					       unsigned int nr_bits)
>  {
> -	/* n is a prior cpu */
> -	cpu_max_bits_warn(n + 1, nr_bits);
> +	/* -1 is a legal arg here. */
> +	if (n != -1)
> +		cpu_max_bits_warn(n, nr_bits);
>  
>  	if (srcp)
>  		return find_next_bit(srcp, nr_bits, n + 1);
> @@ -3685,8 +3686,9 @@ static inline int netif_attrmask_next_and(int n, const unsigned long *src1p,
>  					  const unsigned long *src2p,
>  					  unsigned int nr_bits)
>  {
> -	/* n is a prior cpu */
> -	cpu_max_bits_warn(n + 1, nr_bits);
> +	/* -1 is a legal arg here. */
> +	if (n != -1)
> +		cpu_max_bits_warn(n, nr_bits);
>  
>  	if (src1p && src2p)
>  		return find_next_and_bit(src1p, src2p, nr_bits, n + 1);
> -- 
> 2.34.1