From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 2/3] tun: free skb in early errors Date: Fri, 1 Dec 2017 16:36:49 +0200 Message-ID: <20171201163220-mutt-send-email-mst@kernel.org> References: <1512107669-27572-1-git-send-email-wexu@redhat.com> <1512107669-27572-3-git-send-email-wexu@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: wexu@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mjrosato@linux.vnet.ibm.com To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Dec 01, 2017 at 03:07:44PM +0800, Jason Wang wrote: > > > On 2017年12月01日 13:54, wexu@redhat.com wrote: > > From: Wei Xu > > > > 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 > > Reported-by: Matthew Rosato > > --- > > 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;