[PATCH] VSOCK: bind to random port for VMADDR_PORT_ANY

[PATCH] VSOCK: bind to random port for VMADDR_PORT_ANY

[Lepton Wu]

The old code always starts from fixed port for VMADDR_PORT_ANY. Sometimes
when VMM crashed, there is still orphaned vsock which is waiting for
close timer, then it could cause connection time out for new started VM
if they are trying to connect to same port with same guest cid since the
new packets could hit that orphaned vsock. We could also fix this by doing
more in vhost_vsock_reset_orphans, but any way, it should be better to start
from a random local port instead of a fixed one.

Signed-off-by: Lepton Wu <ytht.net@gmail.com>
---
 net/vmw_vsock/af_vsock.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index ab27a2872935..73817e846a1f 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -107,6 +107,7 @@
 #include <linux/mutex.h>
 #include <linux/net.h>
 #include <linux/poll.h>
+#include <linux/random.h>
 #include <linux/skbuff.h>
 #include <linux/smp.h>
 #include <linux/socket.h>
@@ -504,9 +505,12 @@ static void vsock_pending_work(struct work_struct *work)
 static int __vsock_bind_stream(struct vsock_sock *vsk,
 			       struct sockaddr_vm *addr)
 {
-	static u32 port = LAST_RESERVED_PORT + 1;
+	static u32 port = 0;
 	struct sockaddr_vm new_addr;
 
+	if (!port)
+		port = prandom_u32();
+
 	vsock_addr_init(&new_addr, addr->svm_cid, addr->svm_port);
 
 	if (addr->svm_port == VMADDR_PORT_ANY) {
-- 
2.20.0.rc2.403.gdbc3b29805-goog

Re: [PATCH] VSOCK: bind to random port for VMADDR_PORT_ANY

[Greg KH]

On Mon, Dec 10, 2018 at 06:06:31PM -0800, Lepton Wu wrote:
> The old code always starts from fixed port for VMADDR_PORT_ANY. Sometimes
> when VMM crashed, there is still orphaned vsock which is waiting for
> close timer, then it could cause connection time out for new started VM
> if they are trying to connect to same port with same guest cid since the
> new packets could hit that orphaned vsock. We could also fix this by doing
> more in vhost_vsock_reset_orphans, but any way, it should be better to start
> from a random local port instead of a fixed one.
> 
> Signed-off-by: Lepton Wu <ytht.net@gmail.com>
> ---
>  net/vmw_vsock/af_vsock.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>