| Message ID | 1587872115-42805-1-git-send-email-xiyuyang19@fudan.edu.cn |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [v2] bpf: Fix sk_psock refcnt leak when receiving message | expand |
On Sun, Apr 26, 2020 at 05:35 AM CEST, Xiyu Yang wrote: > tcp_bpf_recvmsg() invokes sk_psock_get(), which returns a reference of > the specified sk_psock object to "psock" with increased refcnt. > > When tcp_bpf_recvmsg() returns, local variable "psock" becomes invalid, > so the refcount should be decreased to keep refcount balanced. > > The reference counting issue happens in several exception handling paths > of tcp_bpf_recvmsg(). When those error scenarios occur such as "flags" > includes MSG_ERRQUEUE, the function forgets to decrease the refcnt > increased by sk_psock_get(), causing a refcnt leak. > > Fix this issue by calling sk_psock_put() or pulling up the error queue > read handling when those error scenarios occur. > > Fixes: e7a5f1f1cd000 ("bpf/sockmap: Read psock ingress_msg before sk_receive_queue") > Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn> > Signed-off-by: Xin Tan <tanxin.ctf@gmail.com> > --- > Changes in v2: > - Add Fixes tag > - Pull up the error queue read handling > --- > net/ipv4/tcp_bpf.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c > index 5a05327f97c1..ff96466ea6da 100644 > --- a/net/ipv4/tcp_bpf.c > +++ b/net/ipv4/tcp_bpf.c > @@ -262,14 +262,17 @@ static int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, > struct sk_psock *psock; > int copied, ret; > > + if (unlikely(flags & MSG_ERRQUEUE)) > + return inet_recv_error(sk, msg, len, addr_len); > + > psock = sk_psock_get(sk); > if (unlikely(!psock)) > return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len); > - if (unlikely(flags & MSG_ERRQUEUE)) > - return inet_recv_error(sk, msg, len, addr_len); > if (!skb_queue_empty(&sk->sk_receive_queue) && > - sk_psock_queue_empty(psock)) > + sk_psock_queue_empty(psock)) { > + sk_psock_put(sk, psock); > return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len); > + } > lock_sock(sk); > msg_bytes_ready: > copied = __tcp_bpf_recvmsg(sk, psock, msg, len, flags); Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
On 4/26/20 5:35 AM, Xiyu Yang wrote: > tcp_bpf_recvmsg() invokes sk_psock_get(), which returns a reference of > the specified sk_psock object to "psock" with increased refcnt. > > When tcp_bpf_recvmsg() returns, local variable "psock" becomes invalid, > so the refcount should be decreased to keep refcount balanced. > > The reference counting issue happens in several exception handling paths > of tcp_bpf_recvmsg(). When those error scenarios occur such as "flags" > includes MSG_ERRQUEUE, the function forgets to decrease the refcnt > increased by sk_psock_get(), causing a refcnt leak. > > Fix this issue by calling sk_psock_put() or pulling up the error queue > read handling when those error scenarios occur. > > Fixes: e7a5f1f1cd000 ("bpf/sockmap: Read psock ingress_msg before sk_receive_queue") > Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn> > Signed-off-by: Xin Tan <tanxin.ctf@gmail.com> Applied, thanks!
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index 5a05327f97c1..ff96466ea6da 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -262,14 +262,17 @@ static int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, struct sk_psock *psock; int copied, ret; + if (unlikely(flags & MSG_ERRQUEUE)) + return inet_recv_error(sk, msg, len, addr_len); + psock = sk_psock_get(sk); if (unlikely(!psock)) return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len); - if (unlikely(flags & MSG_ERRQUEUE)) - return inet_recv_error(sk, msg, len, addr_len); if (!skb_queue_empty(&sk->sk_receive_queue) && - sk_psock_queue_empty(psock)) + sk_psock_queue_empty(psock)) { + sk_psock_put(sk, psock); return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len); + } lock_sock(sk); msg_bytes_ready: copied = __tcp_bpf_recvmsg(sk, psock, msg, len, flags);
tcp_bpf_recvmsg() invokes sk_psock_get(), which returns a reference of the specified sk_psock object to "psock" with increased refcnt. When tcp_bpf_recvmsg() returns, local variable "psock" becomes invalid, so the refcount should be decreased to keep refcount balanced. The reference counting issue happens in several exception handling paths of tcp_bpf_recvmsg(). When those error scenarios occur such as "flags" includes MSG_ERRQUEUE, the function forgets to decrease the refcnt increased by sk_psock_get(), causing a refcnt leak. Fix this issue by calling sk_psock_put() or pulling up the error queue read handling when those error scenarios occur. Fixes: e7a5f1f1cd000 ("bpf/sockmap: Read psock ingress_msg before sk_receive_queue") Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com> --- Changes in v2: - Add Fixes tag - Pull up the error queue read handling --- net/ipv4/tcp_bpf.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)