Re: [PATCH 1/2] taskstats: return -EBADF when cgroupstats receives an invalid fd

[Balbir Singh]

On 7/11/26 6:07 AM, Yiyang Chen wrote:
> cgroupstats_user_cmd() returns 0 without sending a reply or a netlink
> error when the fd passed via CGROUPSTATS_CMD_ATTR_FD does not resolve
> to an open file in the caller's table.  As a result:
> 
> - clients that did not set NLM_F_ACK block on recv() indefinitely
> waiting for a CGROUPSTATS_CMD_NEW message that is never emitted;
> - clients that set NLM_F_ACK receive a misleading "success" ACK
> (errno == 0) with no statistics payload.
> 
> Return -EBADF instead so the netlink layer propagates the error to
> userspace as expected.
> 
> Signed-off-by: Yiyang Chen <cyyzero16@xxxxxxxxx>
> ---
>  kernel/taskstats.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/taskstats.c b/kernel/taskstats.c
> index 2cd0172d0516..8d115670a3ca 100644
> --- a/kernel/taskstats.c
> +++ b/kernel/taskstats.c
> @@ -423,7 +423,7 @@ static int cgroupstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
>  	fd = nla_get_u32(info->attrs[CGROUPSTATS_CMD_ATTR_FD]);
>  	CLASS(fd, f)(fd);
>  	if (fd_empty(f))
> -		return 0;
> +		return -EBADF;
>  
>  	size = nla_total_size(sizeof(struct cgroupstats));
>  

Thanks!

Acked-by: Balbir Singh <balbirs@xxxxxxxxxx>