[PATCH 5.18 029/102] net: tun: stop NAPI when detaching queues

Greg Kroah-Hartman
2022-07-05T12:31:10Z

From: Jakub Kicinski <kuba@kernel.org>

commit a8fc8cb5692aebb9c6f7afd4265366d25dcd1d01 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/tun.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -274,6 +274,12 @@ static void tun_napi_init(struct tun_str
}
}

+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)
@@ -654,8 +660,10 @@ static void __tun_detach(struct tun_file
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);
@@ -809,6 +817,7 @@ static int tun_attach(struct tun_struct

if (tfile->detached) {
tun_enable_queue(tfile);
+ tun_napi_enable(tfile);
} else {
sock_hold(&tfile->sk);
tun_napi_init(tun, tfile, napi, napi_frags);