On Thu, Aug 17, 2023 at 03:08:47PM -0400, Gabriel Krisman Bertazi wrote:
> Breno Leitao <leitao@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> > 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?
Not really, sock->ops->getsockopt() does not suport sockptr_t, but
__user addresses, differently from setsockopt()
int (*setsockopt)(struct socket *sock, int level,
int optname, sockptr_t optval,
unsigned int optlen);
int (*getsockopt)(struct socket *sock, int level,
int optname, char __user *optval, int __user *optlen);
In order to be able to call sock->ops->getsockopt(), the callback
function will need to accepted sockptr.
