On Fri, Dec 01, 2017 at 03:07:44PM +0800, Jason Wang wrote:
>
>
> On 2017年12月01日 13:54, wexu@xxxxxxxxxx wrote:
> > From: Wei Xu <wexu@xxxxxxxxxx>
> >
> > tun_recvmsg() supports accepting skb by msg_control after
> > commit ac77cfd4258f ("tun: support receiving skb through msg_control"),
> > the skb if presented should be freed within the function, otherwise it
> > would be leaked.
> >
> > Signed-off-by: Wei Xu <wexu@xxxxxxxxxx>
> > Reported-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/net/tun.c | 14 +++++++++++---
> > 1 file changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index 6a7bde9..5563430 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -2067,14 +2067,17 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
> > {
> > struct tun_file *tfile = container_of(sock, struct tun_file, socket);
> > struct tun_struct *tun = tun_get(tfile);
> > + struct sk_buff *skb = m->msg_control;
> > int ret;
> > - if (!tun)
> > - return -EBADFD;
> > + if (!tun) {
> > + ret = -EBADFD;
> > + goto out_free_skb;
>
> Unfortunately, you can't to there since tun is NULL.
Right, this should just be kfree_skb(skb); return -EBADFD;
>
> > + }
> > if (flags & ~(MSG_DONTWAIT|MSG_TRUNC|MSG_ERRQUEUE)) {
> > ret = -EINVAL;
> > - goto out;
> > + goto out_free_skb;
> > }
> > if (flags & MSG_ERRQUEUE) {
> > ret = sock_recv_errqueue(sock->sk, m, total_len,
> > @@ -2087,6 +2090,11 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
> > m->msg_flags |= MSG_TRUNC;
> > ret = flags & MSG_TRUNC ? ret : total_len;
> > }
> > + goto out;
>
> We usually don't use goto in the case of success, and you need deal with the
> case skb != NULL but iov_iter_count(to) == 0 in tun_do_read().
>
> Thanks
I agree, the way to lay this out is:
tun_put(tun);
return ret;
err:
tun_put(tun);
err_tun:
if (skb)
kfree_skb(skb);
return ret;
> > +
> > +out_free_skb:
> > + if (skb)
> > + kfree_skb(skb);
> > out:
> > tun_put(tun);
> > return ret;
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