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

[Breno Leitao <leitao@debian.org>]

Hello Gabriel,

On Wed, Aug 09, 2023 at 12:46:27PM -0400, Gabriel Krisman Bertazi wrote:
> Breno Leitao <leitao@debian.org> 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 <leitao@debian.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 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?

I think that checking ctx->compat seems to be the right thing to do. I
will update.