Re: [PATCH] tap: fix net_init_tap() return code

[Jason Wang]

在 2023/4/5 23:38, Steven Sistare 写道:
> On 4/4/2023 6:00 PM, Philippe Mathieu-Daudé wrote:
> > On 4/4/23 18:00, Steve Sistare wrote:
> > > When net_init_tap() succeeds for a multi-queue device, it returns a
> > > non-zero ret=1 code to its caller, because of this code where ret becomes
> > Indeed g_unix_set_fd_nonblocking() returns TRUE on success.
> >
> > Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> >
> > > 1 when g_unix_set_fd_nonblocking succeeds.  Luckily, the only current call
> > > site checks for negative, rather than non-zero.
> > >
> > >       ret = g_unix_set_fd_nonblocking(fd, true, NULL);
> > >       if (!ret) {
> > >           ...
> > >           goto free_fail;
> > >
> > > Also, if g_unix_set_fd_nonblocking fails (though unlikely), ret=0 is returned,
> > > and the caller will use a broken interface.
> > We should return -1 from free_fail, not trying to propagate 'ret':
> Thanks for the review.  I will add your "return -1" changes if Jason agrees.
>
> - Steve


Note that the "free_fail" label is kind of ambiguous. It is used even if 
we succeed if I was not wrong.

Thanks


> > -- >8 --
> > diff --git a/net/tap.c b/net/tap.c
> > index 1bf085d422..e59238bda0 100644
> > --- a/net/tap.c
> > +++ b/net/tap.c
> > @@ -821,3 +821,2 @@ int net_init_tap(const Netdev *netdev, const char *name,
> >       char ifname[128];
> > -    int ret = 0;
> >
> > @@ -896,3 +895,2 @@ int net_init_tap(const Netdev *netdev, const char *name,
> >                              "the number of vhostfds passed");
> > -                ret = -1;
> >                   goto free_fail;
> > @@ -904,3 +902,2 @@ int net_init_tap(const Netdev *netdev, const char *name,
> >               if (fd == -1) {
> > -                ret = -1;
> >                   goto free_fail;
> > @@ -908,4 +905,3 @@ int net_init_tap(const Netdev *netdev, const char *name,
> >
> > -            ret = g_unix_set_fd_nonblocking(fd, true, NULL);
> > -            if (!ret) {
> > +            if (!g_unix_set_fd_nonblocking(fd, true, NULL)) {
> >                   error_setg_errno(errp, errno, "%s: Can't use file descriptor 
> > %d",
> > @@ -918,3 +914,2 @@ int net_init_tap(const Netdev *netdev, const char *name,
> >                   if (vnet_hdr < 0) {
> > -                    ret = -1;
> >                       goto free_fail;
> > @@ -924,3 +919,2 @@ int net_init_tap(const Netdev *netdev, const char *name,
> >                              "vnet_hdr not consistent across given tap fds");
> > -                ret = -1;
> >                   goto free_fail;
> > @@ -934,3 +928,2 @@ int net_init_tap(const Netdev *netdev, const char *name,
> >                   error_propagate(errp, err);
> > -                ret = -1;
> >                   goto free_fail;
> > @@ -948,3 +941,3 @@ free_fail:
> >           g_free(vhost_fds);
> > -        return ret;
> > +        return -1;
> >       } else if (tap->helper) {
> > ---
> >
> > > Fixes: a8208626ba89.. ("net: replace qemu_set_nonblock()")
> > > Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> > > ---
> > >    net/tap.c | 4 ++--
> > >    1 file changed, 2 insertions(+), 2 deletions(-)