Patch "net/packet: convert po->auxdata to an atomic flag" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    net/packet: convert po->auxdata to an atomic flag

to the 5.4-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:
     net-packet-convert-po-auxdata-to-an-atomic-flag.patch
and it can be found in the queue-5.4 subdirectory.

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



commit 3b04dee448a9219a13e788b77e06cd7df0232331
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Thu Mar 16 01:10:08 2023 +0000

    net/packet: convert po->auxdata to an atomic flag
    
    [ Upstream commit fd53c297aa7b077ae98a3d3d2d3aa278a1686ba6 ]
    
    po->auxdata can be read while another thread
    is changing its value, potentially raising KCSAN splat.
    
    Convert it to PACKET_SOCK_AUXDATA flag.
    
    Fixes: 8dc419447415 ("[PACKET]: Add optional checksum computation for recvmsg")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 0e88a8dd4530f..13666fe787db7 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3456,7 +3456,7 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 		memcpy(msg->msg_name, &PACKET_SKB_CB(skb)->sa, copy_len);
 	}
 
-	if (pkt_sk(sk)->auxdata) {
+	if (packet_sock_flag(pkt_sk(sk), PACKET_SOCK_AUXDATA)) {
 		struct tpacket_auxdata aux;
 
 		aux.tp_status = TP_STATUS_USER;
@@ -3839,9 +3839,7 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
 		if (copy_from_user(&val, optval, sizeof(val)))
 			return -EFAULT;
 
-		lock_sock(sk);
-		po->auxdata = !!val;
-		release_sock(sk);
+		packet_sock_flag_set(po, PACKET_SOCK_AUXDATA, val);
 		return 0;
 	}
 	case PACKET_ORIGDEV:
@@ -4002,7 +4000,7 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
 
 		break;
 	case PACKET_AUXDATA:
-		val = po->auxdata;
+		val = packet_sock_flag(po, PACKET_SOCK_AUXDATA);
 		break;
 	case PACKET_ORIGDEV:
 		val = packet_sock_flag(po, PACKET_SOCK_ORIGDEV);
diff --git a/net/packet/diag.c b/net/packet/diag.c
index e1ac9bb375b31..d704c7bf51b20 100644
--- a/net/packet/diag.c
+++ b/net/packet/diag.c
@@ -23,7 +23,7 @@ static int pdiag_put_info(const struct packet_sock *po, struct sk_buff *nlskb)
 	pinfo.pdi_flags = 0;
 	if (po->running)
 		pinfo.pdi_flags |= PDI_RUNNING;
-	if (po->auxdata)
+	if (packet_sock_flag(po, PACKET_SOCK_AUXDATA))
 		pinfo.pdi_flags |= PDI_AUXDATA;
 	if (packet_sock_flag(po, PACKET_SOCK_ORIGDEV))
 		pinfo.pdi_flags |= PDI_ORIGDEV;
diff --git a/net/packet/internal.h b/net/packet/internal.h
index 23649010e9586..2b2b85dadf8ea 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -117,8 +117,7 @@ struct packet_sock {
 	struct mutex		pg_vec_lock;
 	unsigned long		flags;
 	unsigned int		running;	/* bind_lock must be held */
-	unsigned int		auxdata:1,	/* writer must hold sock lock */
-				has_vnet_hdr:1,
+	unsigned int		has_vnet_hdr:1, /* writer must hold sock lock */
 				tp_loss:1,
 				tp_tx_has_off:1;
 	int			pressure;
@@ -145,6 +144,7 @@ static struct packet_sock *pkt_sk(struct sock *sk)
 
 enum packet_sock_flags {
 	PACKET_SOCK_ORIGDEV,
+	PACKET_SOCK_AUXDATA,
 };
 
 static inline void packet_sock_flag_set(struct packet_sock *po,