netdev - [PATCH net-next 3/9] net/packet: convert po->auxdata to an atomic flag

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Message-ID: <20230316011014.992179-4-edumazet@google.com>
Date:   Thu, 16 Mar 2023 01:10:08 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, Willem de Bruijn <willemb@...gle.com>,
        eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 3/9] net/packet: convert po->auxdata to an atomic flag

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@...gle.com>
---
 net/packet/af_packet.c | 8 +++-----
 net/packet/diag.c      | 2 +-
 net/packet/internal.h  | 4 ++--
 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index af7c44169b869dc65be293c5594edba919a7fe4b..ecd9fc27e360cc85be35de568e6ebcb2dbbd9d39 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3514,7 +3514,7 @@ 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;
@@ -3900,9 +3900,7 @@ packet_setsockopt(struct socket *sock, int level, int optname, sockptr_t optval,
 		if (copy_from_sockptr(&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:
@@ -4060,7 +4058,7 @@ 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 e1ac9bb375b313dbb4af9a4f9aa3cf5fe7e0f47e..d704c7bf51b2073f792ff35c1f46fba251dd4761 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 178cd1852238d39596acbc58afa0ce12159663d1..3bae8ea7a36f523d554177acfb6b6e960ba6965c 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -118,8 +118,7 @@ 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;
@@ -146,6 +145,7 @@ static inline 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,
-- 
2.40.0.rc2.332.ga46443480c-goog