Re: [PATCH] tun: Fix use-after-free in tun_net_xmit

[Cong Wang]

On Mon, Apr 29, 2019 at 7:55 AM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> The problem seems real enough, but an extra synchronize_net on tun_attach
> might be a problem, slowing guest startup significantly.
> Better ideas?

Yes, I proposed the following patch in the other thread.

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index e9ca1c088d0b..31c3210288cb 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -3431,6 +3431,7 @@ static int tun_chr_open(struct inode *inode,
struct file * file)
        file->private_data = tfile;
        INIT_LIST_HEAD(&tfile->next);

+       sock_set_flag(&tfile->sk, SOCK_RCU_FREE);
        sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);

        return 0;