[PATCH net] netdev: fix double-free in netdev_nl_bind_rx_doit()

[PATCH net] netdev: fix double-free in netdev_nl_bind_rx_doit()

[Jakub Kicinski]

Sashiko flags that genlmsg_reply() always consumes the skb.
The error path calls nlmsg_free(rsp) so we can't jump directly
to it. Let's not unbind, just propagate the error to the user.
This is the typical way of handling genlmsg_reply() failures.
They shouldn't happen unless user does something silly like
calling the kernel with an already-full rcvbuf.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Fixes: 170aafe35cb9 ("netdev: support binding dma-buf to netdevice")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: bobbyeshleman@gmail.com
CC: dw@davidwei.uk
CC: daniel@iogearbox.net
CC: razor@blackwall.org
CC: sdf@fomichev.me
CC: willemb@google.com
CC: kaiyuanz@google.com
---
 net/core/netdev-genl.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index b4d48f3672a5..11b0b91683d7 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1095,8 +1095,6 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
 	genlmsg_end(rsp, hdr);
 
 	err = genlmsg_reply(rsp, info);
-	if (err)
-		goto err_unbind;
 
 	bitmap_free(rxq_bitmap);
 
@@ -1104,7 +1102,7 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
 
 	mutex_unlock(&priv->lock);
 
-	return 0;
+	return err < 0 ? err : 0;
 
 err_unbind:
 	net_devmem_unbind_dmabuf(binding);
-- 
2.54.0