tun: use socket locks for sk_{attach,detatch}_filter

This reverts commit 5a5abb1fa3b05dd ("tun, bpf: fix suspicious RCU usage
in tun_{attach, detach}_filter") and replaces it to use lock_sock around
sk_{attach,detach}_filter. The checks inside filter.c are updated with
lockdep_sock_is_held to check for proper socket locks.

It keeps the code cleaner by ensuring that only one lock governs the
socket filter instead of two independent locks.

Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 5 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9abc36bf77ea..64bc143eddd9 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -622,8 +622,9 @@ static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filte
 
         /* Re-attach the filter to persist device */
         if (!skip_filter && (tun->filter_attached == true)) {
-                err = __sk_attach_filter(&tun->fprog, tfile->socket.sk,
-                                         lockdep_rtnl_is_held());
+                lock_sock(tfile->socket.sk);
+                err = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+                release_sock(tfile->socket.sk);
                 if (!err)
                         goto out;
         }
@@ -1824,7 +1825,9 @@ static void tun_detach_filter(struct tun_struct *tun, int n)
 
         for (i = 0; i < n; i++) {
                 tfile = rtnl_dereference(tun->tfiles[i]);
-                __sk_detach_filter(tfile->socket.sk, lockdep_rtnl_is_held());
+                lock_sock(tfile->socket.sk);
+                sk_detach_filter(tfile->socket.sk);
+                release_sock(tfile->socket.sk);
         }
 
         tun->filter_attached = false;
@@ -1837,8 +1840,9 @@ static int tun_attach_filter(struct tun_struct *tun)
 
         for (i = 0; i < tun->numqueues; i++) {
                 tfile = rtnl_dereference(tun->tfiles[i]);
-                ret = __sk_attach_filter(&tun->fprog, tfile->socket.sk,
-                                         lockdep_rtnl_is_held());
+                lock_sock(tfile->socket.sk);
+                ret = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+                release_sock(tfile->socket.sk);
                 if (ret) {
                         tun_detach_filter(tun, i);
                         return ret;