net: tun: stop NAPI when detaching queues

While looking at a syzbot report I noticed the NAPI only gets
disabled before it's deleted. I think that user can detach
the queue before destroying the device and the NAPI will never
be stopped.

Fixes: 943170998b20 ("tun: enable NAPI for TUN/TAP driver")
Acked-by: Petar Penkov <ppenkov@aviatrix.com>
Link: https://lore.kernel.org/r/20220623042105.2274812-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 7fd0288..e2eb358 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -273,6 +273,12 @@ static void tun_napi_init(struct tun_struct *tun, struct tun_file *tfile,
        }
 }
 
+static void tun_napi_enable(struct tun_file *tfile)
+{
+       if (tfile->napi_enabled)
+               napi_enable(&tfile->napi);
+}
+
 static void tun_napi_disable(struct tun_file *tfile)
 {
        if (tfile->napi_enabled)
@@ -653,8 +659,10 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
                if (clean) {
                        RCU_INIT_POINTER(tfile->tun, NULL);
                        sock_put(&tfile->sk);
-               } else
+               } else {
                        tun_disable_queue(tun, tfile);
+                       tun_napi_disable(tfile);
+               }
 
                synchronize_net();
                tun_flow_delete_by_queue(tun, tun->numqueues + 1);
@@ -808,6 +816,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file,
 
        if (tfile->detached) {
                tun_enable_queue(tfile);
+               tun_napi_enable(tfile);
        } else {
                sock_hold(&tfile->sk);
                tun_napi_init(tun, tfile, napi, napi_frags);