netdev - Re: [PATCH v3 8/9] io_uring/cmd: BPF hook for getsockopt cmd

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Date: Thu, 17 Aug 2023 15:08:47 -0400
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: Breno Leitao <leitao@...ian.org>
Cc: sdf@...gle.com,  axboe@...nel.dk,  asml.silence@...il.com,
  willemdebruijn.kernel@...il.com,  martin.lau@...ux.dev,
  bpf@...r.kernel.org,  linux-kernel@...r.kernel.org,
  netdev@...r.kernel.org,  io-uring@...r.kernel.org,  kuba@...nel.org,
  pabeni@...hat.com
Subject: Re: [PATCH v3 8/9] io_uring/cmd: BPF hook for getsockopt cmd

Breno Leitao <leitao@...ian.org> writes:

> Add BPF hook support for getsockopts io_uring command. So, BPF cgroups
> programs can run when SOCKET_URING_OP_GETSOCKOPT command is executed
> through io_uring.
>
> 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 <leitao@...ian.org>
> ---
>  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 a567dd32df00..9e08a14760c3 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>
> @@ -184,17 +186,23 @@ 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 (!(issue_flags & IO_URING_F_COMPAT))
> +		err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level,
> +						     optname,
> +						     USER_SOCKPTR(optval),
> +						     KERNEL_SOCKPTR(&optlen),
> +						     optlen, err);
> +
> +	if (!err)
>  		return optlen;
> -	}

Shouldn't you call sock->ops->getsockopt for level!=SOL_SOCKET prior to
running the hook?  Before this patch, it would bail out with EOPNOTSUPP,
but now the bpf hook gets called even for level!=SOL_SOCKET, which
doesn't fit __sys_getsockopt. Am I misreading the code?

-- 
Gabriel Krisman Bertazi