Subject: Re: [PATCH v2 7/8] io_uring/cmd: BPF hook for getsockopt cmd

From: Gabriel Krisman Bertazi <[email-masked]>
Date: Wed, 09 Aug 2023 12:46:27 -0400

Breno Leitao <[email-masked]> writes:

> Add BPF hooks support for getsockopts io_uring command. So, bpf cgroups
> programs can run when SOCKET_URING_OP_GETSOCKOPT command is called.
>
> This implementation follows a similar approach to what
> __sys_getsockopt() does, but, using USER_SOCKPTR() for optval instead of
> kernel pointer.
>
> Signed-off-by: Breno Leitao <[email-masked]>
> ---
>  io_uring/uring_cmd.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
> index dbba005a7290..3693e5779229 100644
> --- a/io_uring/uring_cmd.c
> +++ b/io_uring/uring_cmd.c
> @@ -5,6 +5,8 @@
>  #include <linux/io_uring.h>
>  #include <linux/security.h>
>  #include <linux/nospec.h>
> +#include <linux/compat.h>
> +#include <linux/bpf-cgroup.h>
>  
>  #include <uapi/linux/io_uring.h>
>  #include <uapi/asm-generic/ioctls.h>
> @@ -179,17 +181,23 @@ static inline int io_uring_cmd_getsockopt(struct socket *sock,
>  	if (err)
>  		return err;
>  
> -	if (level == SOL_SOCKET) {
> +	err = -EOPNOTSUPP;
> +	if (level == SOL_SOCKET)
>  		err = sk_getsockopt(sock->sk, level, optname,
>  				    USER_SOCKPTR(optval),
>  				    KERNEL_SOCKPTR(&optlen));
> -		if (err)
> -			return err;
>  
> +	if (!in_compat_syscall())
> +		err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level,
> +						     optname,
> +						     USER_SOCKPTR(optval),
> +						     KERNEL_SOCKPTR(&optlen),
> +						     optlen, err);

I'm not sure if it makes sense to use in_compat_syscall() here.  Can't
this be invoked in a ring with ctx->compat set, but from outside a
compat syscall context (i.e. from sqpoll or even a !compat
io_uring_enter syscall)? I suspect you might need to check ctx->compact
instead, but I'm not sure. Did you consider that?

> +
> +	if (!err)
>  		return optlen;
> -	}
>  
> -	return -EOPNOTSUPP;
> +	return err;
>  }
>  
>  static inline int io_uring_cmd_setsockopt(struct socket *sock,

-- 
Gabriel Krisman Bertazi