linux-kernel - [PATCH 5.8 383/464] af_packet: TPACKET_V3: fix fill status rwlock imbalance

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Date:   Mon, 17 Aug 2020 17:15:36 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, John Ogness <john.ogness@...utronix.de>,
        kernel test robot <lkp@...el.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.8 383/464] af_packet: TPACKET_V3: fix fill status rwlock imbalance

From: John Ogness <john.ogness@...utronix.de>

[ Upstream commit 88fd1cb80daa20af063bce81e1fad14e945a8dc4 ]

After @blk_fill_in_prog_lock is acquired there is an early out vnet
situation that can occur. In that case, the rwlock needs to be
released.

Also, since @blk_fill_in_prog_lock is only acquired when @tp_version
is exactly TPACKET_V3, only release it on that exact condition as
well.

And finally, add sparse annotation so that it is clearer that
prb_fill_curr_block() and prb_clear_blk_fill_status() are acquiring
and releasing @blk_fill_in_prog_lock, respectively. sparse is still
unable to understand the balance, but the warnings are now on a
higher level that make more sense.

Fixes: 632ca50f2cbd ("af_packet: TPACKET_V3: replace busy-wait loop")
Signed-off-by: John Ogness <john.ogness@...utronix.de>
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/packet/af_packet.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -942,6 +942,7 @@ static int prb_queue_frozen(struct tpack
 }
 
 static void prb_clear_blk_fill_status(struct packet_ring_buffer *rb)
+	__releases(&pkc->blk_fill_in_prog_lock)
 {
 	struct tpacket_kbdq_core *pkc  = GET_PBDQC_FROM_RB(rb);
 	atomic_dec(&pkc->blk_fill_in_prog);
@@ -989,6 +990,7 @@ static void prb_fill_curr_block(char *cu
 				struct tpacket_kbdq_core *pkc,
 				struct tpacket_block_desc *pbd,
 				unsigned int len)
+	__acquires(&pkc->blk_fill_in_prog_lock)
 {
 	struct tpacket3_hdr *ppd;
 
@@ -2286,8 +2288,11 @@ static int tpacket_rcv(struct sk_buff *s
 	if (do_vnet &&
 	    virtio_net_hdr_from_skb(skb, h.raw + macoff -
 				    sizeof(struct virtio_net_hdr),
-				    vio_le(), true, 0))
+				    vio_le(), true, 0)) {
+		if (po->tp_version == TPACKET_V3)
+			prb_clear_blk_fill_status(&po->rx_ring);
 		goto drop_n_account;
+	}
 
 	if (po->tp_version <= TPACKET_V2) {
 		packet_increment_rx_head(po, &po->rx_ring);
@@ -2393,7 +2398,7 @@ static int tpacket_rcv(struct sk_buff *s
 		__clear_bit(slot_id, po->rx_ring.rx_owner_map);
 		spin_unlock(&sk->sk_receive_queue.lock);
 		sk->sk_data_ready(sk);
-	} else {
+	} else if (po->tp_version == TPACKET_V3) {
 		prb_clear_blk_fill_status(&po->rx_ring);
 	}