linux-kernel - [PATCH AUTOSEL 4.19 14/32] net: atlantic: fix use after free kasan warn

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Date:   Mon,  2 Mar 2020 21:48:33 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Pavel Belous <pbelous@...vell.com>,
        Christophe Vu-Brugier <cvubrugier@...tmail.fm>,
        Igor Russkikh <irusskikh@...vell.com>,
        Dmitry Bogdanov <dbogdanov@...vell.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 14/32] net: atlantic: fix use after free kasan warn

From: Pavel Belous <pbelous@...vell.com>

[ Upstream commit a4980919ad6a7be548d499bc5338015e1a9191c6 ]

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@...tmail.fm>
Signed-off-by: Igor Russkikh <irusskikh@...vell.com>
Signed-off-by: Pavel Belous <pbelous@...vell.com>
Signed-off-by: Dmitry Bogdanov <dbogdanov@...vell.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.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(-)

diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
index 8cc34b0bedc3a..d1de11b575f44 100644
--- a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
@@ -530,10 +530,6 @@ int aq_nic_xmit(struct aq_nic_s *self, struct sk_buff *skb)
 	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;
 	}
diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_ring.c b/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
index b3c7994d73eb1..b03e5fd4327e3 100644
--- a/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
@@ -162,9 +162,12 @@ bool aq_ring_tx_clean(struct aq_ring_s *self)
 			}
 		}
 
-		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);
-- 
2.20.1