Re: [PATCH v2 bpf] tools: bpftool: Add missing close before bpftool net attach exit

[wanghai (M)]

在 2020/11/10 12:33, John Fastabend 写道:
> Wang Hai wrote:
> > progfd is created by prog_parse_fd(), before 'bpftool net attach' exit,
> > it should be closed.
> >
> > Fixes: 04949ccc273e ("tools: bpftool: add net attach command to attach XDP on interface")
> > Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
> > ---
> > v1->v2: use cleanup tag instead of repeated closes
> >   tools/bpf/bpftool/net.c | 14 ++++++++------
> >   1 file changed, 8 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
> > index 910e7bac6e9e..1ac7228167e6 100644
> > --- a/tools/bpf/bpftool/net.c
> > +++ b/tools/bpf/bpftool/net.c
> > @@ -578,8 +578,8 @@ static int do_attach(int argc, char **argv)
> >   
> >   	ifindex = net_parse_dev(&argc, &argv);
> >   	if (ifindex < 1) {
> > -		close(progfd);
> > -		return -EINVAL;
> > +		err = -EINVAL;
> > +		goto cleanup;
> >   	}
> >   
> >   	if (argc) {
> > @@ -587,8 +587,8 @@ static int do_attach(int argc, char **argv)
> >   			overwrite = true;
> >   		} else {
> >   			p_err("expected 'overwrite', got: '%s'?", *argv);
> > -			close(progfd);
> > -			return -EINVAL;
> > +			err = -EINVAL;
> > +			goto cleanup;
> >   		}
> >   	}
> >   
> > @@ -600,13 +600,15 @@ static int do_attach(int argc, char **argv)
> I think now that return value depends on this err it should be 'if (err)'
> otherwise we risk retunring non-zero error code from do_attach which
> will cause programs to fail.
I agree with you. Thanks.
> >   	if (err < 0) {
>          ^^^^^^^^^^^^
>          if (err) {
>
> >   		p_err("interface %s attach failed: %s",
> >   		      attach_type_strings[attach_type], strerror(-err));
> > -		return err;
> > +		goto cleanup;
> >   	}
> >   
> >   	if (json_output)
> >   		jsonw_null(json_wtr);
> >   
> > -	return 0;
>
> Alternatively we could add an 'err = 0' here, but above should never
> return a value >0 as far as I can see.
It's true that 'err > 0' doesn't exist currently , but adding 'err = 0' 
would make the code clearer. Thanks for your advice.
> > +cleanup:
> > +	close(progfd);
> > +	return err;
> >   }
> >   
> >   static int do_detach(int argc, char **argv)
> > --
> > 2.17.1
Can it be fixed like this?

--- a/tools/bpf/bpftool/net.c
+++ b/tools/bpf/bpftool/net.c
@@ -578,8 +578,8 @@ static int do_attach(int argc, char **argv)

        ifindex = net_parse_dev(&argc, &argv);
        if (ifindex < 1) {
-               close(progfd);
-               return -EINVAL;
+               err = -EINVAL;
+               goto cleanup;
        }

        if (argc) {
@@ -587,8 +587,8 @@ static int do_attach(int argc, char **argv)
                        overwrite = true;
                } else {
                        p_err("expected 'overwrite', got: '%s'?", *argv);
-                       close(progfd);
-                       return -EINVAL;
+                       err = -EINVAL;
+                       goto cleanup;
                }
        }

@@ -597,16 +597,19 @@ static int do_attach(int argc, char **argv)
                err = do_attach_detach_xdp(progfd, attach_type, ifindex,
                                           overwrite);

-       if (err < 0) {
+       if (err) {
                p_err("interface %s attach failed: %s",
                      attach_type_strings[attach_type], strerror(-err));
-               return err;
+               goto cleanup;
        }

        if (json_output)
                jsonw_null(json_wtr);

-       return 0;
+       ret = 0;
+cleanup:
+       close(progfd);
+       return err;
 }

> .