Patch "af_packet: do not use READ_ONCE() in packet_bind()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    af_packet: do not use READ_ONCE() in packet_bind()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     af_packet-do-not-use-read_once-in-packet_bind.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d458d0af68a6c01b6f3fc620631726eeac7d2fa0
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Fri May 26 15:43:42 2023 +0000

    af_packet: do not use READ_ONCE() in packet_bind()
    
    [ Upstream commit 6ffc57ea004234d9373c57b204fd10370a69f392 ]
    
    A recent patch added READ_ONCE() in packet_bind() and packet_bind_spkt()
    
    This is better handled by reading pkt_sk(sk)->num later
    in packet_do_bind() while appropriate lock is held.
    
    READ_ONCE() in writers are often an evidence of something being wrong.
    
    Fixes: 822b5a1c17df ("af_packet: Fix data-races of pkt_sk(sk)->num.")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
    Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
    Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230526154342.2533026-1-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 05a0b1d8c3721..ccf84ce41fd71 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3159,6 +3159,9 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
 
 	lock_sock(sk);
 	spin_lock(&po->bind_lock);
+	if (!proto)
+		proto = po->num;
+
 	rcu_read_lock();
 
 	if (po->fanout) {
@@ -3259,7 +3262,7 @@ static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
 	memcpy(name, uaddr->sa_data, sizeof(uaddr->sa_data));
 	name[sizeof(uaddr->sa_data)] = 0;
 
-	return packet_do_bind(sk, name, 0, READ_ONCE(pkt_sk(sk)->num));
+	return packet_do_bind(sk, name, 0, 0);
 }
 
 static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
@@ -3276,8 +3279,7 @@ static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len
 	if (sll->sll_family != AF_PACKET)
 		return -EINVAL;
 
-	return packet_do_bind(sk, NULL, sll->sll_ifindex,
-			      sll->sll_protocol ? : READ_ONCE(pkt_sk(sk)->num));
+	return packet_do_bind(sk, NULL, sll->sll_ifindex, sll->sll_protocol);
 }
 
 static struct proto packet_proto = {