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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Christophe Vu-Brugier <cvubrugier@fastmail.fm>,
        Igor Russkikh <irusskikh@marvell.com>,
        Pavel Belous <pbelous@marvell.com>,
        Dmitry Bogdanov <dbogdanov@marvell.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.4 107/152] net: atlantic: fix use after free kasan warn
Date:   Tue,  3 Mar 2020 18:43:25 +0100
Message-Id: <20200303174314.806720778@linuxfoundation.org>
In-Reply-To: <20200303174302.523080016@linuxfoundation.org>
References: <20200303174302.523080016@linuxfoundation.org>
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From: Pavel Belous <pbelous@marvell.com>

commit a4980919ad6a7be548d499bc5338015e1a9191c6 upstream.

skb->len is used to calculate statistics after xmit invocation.

Under a stress load it may happen that skb will be xmited,
rx interrupt will come and skb will be freed, all before xmit function
is even returned.

Eventually, skb->len will access unallocated area.

Moving stats calculation into tx_clean routine.

Fixes: 018423e90bee ("net: ethernet: aquantia: Add ring support code")
Reported-by: Christophe Vu-Brugier <cvubrugier@fastmail.fm>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: Pavel Belous <pbelous@marvell.com>
Signed-off-by: Dmitry Bogdanov <dbogdanov@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/net/ethernet/aquantia/atlantic/aq_nic.c  |    4 ----
 drivers/net/ethernet/aquantia/atlantic/aq_ring.c |    7 +++++--
 2 files changed, 5 insertions(+), 6 deletions(-)

--- a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
@@ -598,10 +598,6 @@ int aq_nic_xmit(struct aq_nic_s *self, s
 	if (likely(frags)) {
 		err = self->aq_hw_ops->hw_ring_tx_xmit(self->aq_hw,
 						       ring, frags);
-		if (err >= 0) {
-			++ring->stats.tx.packets;
-			ring->stats.tx.bytes += skb->len;
-		}
 	} else {
 		err = NETDEV_TX_BUSY;
 	}
--- a/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
@@ -243,9 +243,12 @@ bool aq_ring_tx_clean(struct aq_ring_s *
 			}
 		}
 
-		if (unlikely(buff->is_eop))
-			dev_kfree_skb_any(buff->skb);
+		if (unlikely(buff->is_eop)) {
+			++self->stats.rx.packets;
+			self->stats.tx.bytes += buff->skb->len;
 
+			dev_kfree_skb_any(buff->skb);
+		}
 		buff->pa = 0U;
 		buff->eop_index = 0xffffU;
 		self->sw_head = aq_ring_next_dx(self, self->sw_head);