[PATCH 4.19 131/168] af_packet: TPACKET_V3: fix fill status rwlock imbalance

Greg Kroah-Hartman
2020-08-17T17:27:18Z

From: John Ogness <john.ogness@linutronix.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@linutronix.de>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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
@@ -949,6 +949,7 @@ 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);
@@ -996,6 +997,7 @@ 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;

@@ -2272,8 +2274,11 @@ 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);
@@ -2379,7 +2384,7 @@ 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);
}