On Mon, Jul 29, 2024 at 10:19 PM <viro@xxxxxxxxxx> wrote:
>
> From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
>
> Irregularity here is fdput() not in the same scope as fdget();
> just fold ____bpf_prog_get() into its (only) caller and that's
> it...
>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> kernel/bpf/syscall.c | 32 +++++++++++---------------------
> 1 file changed, 11 insertions(+), 21 deletions(-)
>
Folding makes total sense, the logic lgtm (though I find CLASS(fd,
f)(ufd) utterly non-intuitive naming-wise). Extra IS_ERR(prog) check
should be dropped though, see below.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 3093bf2cc266..c5b252c0faa8 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2407,18 +2407,6 @@ int bpf_prog_new_fd(struct bpf_prog *prog)
> O_RDWR | O_CLOEXEC);
> }
>
> -static struct bpf_prog *____bpf_prog_get(struct fd f)
> -{
> - if (!fd_file(f))
> - return ERR_PTR(-EBADF);
> - if (fd_file(f)->f_op != &bpf_prog_fops) {
> - fdput(f);
> - return ERR_PTR(-EINVAL);
> - }
> -
> - return fd_file(f)->private_data;
> -}
> -
> void bpf_prog_add(struct bpf_prog *prog, int i)
> {
> atomic64_add(i, &prog->aux->refcnt);
> @@ -2474,20 +2462,22 @@ bool bpf_prog_get_ok(struct bpf_prog *prog,
> static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type *attach_type,
> bool attach_drv)
> {
> - struct fd f = fdget(ufd);
> + CLASS(fd, f)(ufd);
> struct bpf_prog *prog;
>
> - prog = ____bpf_prog_get(f);
> - if (IS_ERR(prog))
> + if (fd_empty(f))
> + return ERR_PTR(-EBADF);
> + if (fd_file(f)->f_op != &bpf_prog_fops)
> + return ERR_PTR(-EINVAL);
> +
> + prog = fd_file(f)->private_data;
> + if (IS_ERR(prog)) // can that actually happen?
no, it can't, private_data will always be a valid pointer, otherwise
that file would never be successfully created
> return prog;
> - if (!bpf_prog_get_ok(prog, attach_type, attach_drv)) {
> - prog = ERR_PTR(-EINVAL);
> - goto out;
> - }
> +
> + if (!bpf_prog_get_ok(prog, attach_type, attach_drv))
> + return ERR_PTR(-EINVAL);
>
> bpf_prog_inc(prog);
> -out:
> - fdput(f);
> return prog;
> }
>
> --
> 2.39.2
>
>
