linux-kernel - [PATCH 4.4 015/192] [PATCH 015/135] e1000: fix data race between tx_ring->next_to

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Message-Id: <20160912152159.553688013@linuxfoundation.org>
Date:   Mon, 12 Sep 2016 18:58:44 +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, Dmitry Vyukov <dvyukov@...gle.com>,
        Aaron Brown <aaron.f.brown@...el.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.4 015/192] [PATCH 015/135] e1000: fix data race between tx_ring->next_to_clean

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 9eab46b7cb8d0b0dcf014bf7b25e0e72b9e4d929 ]

e1000_clean_tx_irq cleans buffers and sets tx_ring->next_to_clean,
then e1000_xmit_frame reuses the cleaned buffers. But there are no
memory barriers when buffers gets recycled, so the recycled buffers
can be corrupted.

Use smp_store_release to update tx_ring->next_to_clean and
smp_load_acquire to read tx_ring->next_to_clean to properly
hand off buffers from e1000_clean_tx_irq to e1000_xmit_frame.

The data race was found with KernelThreadSanitizer (KTSAN).

Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
Tested-by: Aaron Brown <aaron.f.brown@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/intel/e1000/e1000.h      |    7 +++++--
 drivers/net/ethernet/intel/e1000/e1000_main.c |    5 ++++-
 2 files changed, 9 insertions(+), 3 deletions(-)

--- a/drivers/net/ethernet/intel/e1000/e1000.h
+++ b/drivers/net/ethernet/intel/e1000/e1000.h
@@ -213,8 +213,11 @@ struct e1000_rx_ring {
 };
 
 #define E1000_DESC_UNUSED(R)						\
-	((((R)->next_to_clean > (R)->next_to_use)			\
-	  ? 0 : (R)->count) + (R)->next_to_clean - (R)->next_to_use - 1)
+({									\
+	unsigned int clean = smp_load_acquire(&(R)->next_to_clean);	\
+	unsigned int use = READ_ONCE((R)->next_to_use);			\
+	(clean > use ? 0 : (R)->count) + clean - use - 1;		\
+})
 
 #define E1000_RX_DESC_EXT(R, i)						\
 	(&(((union e1000_rx_desc_extended *)((R).desc))[i]))
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -3876,7 +3876,10 @@ static bool e1000_clean_tx_irq(struct e1
 		eop_desc = E1000_TX_DESC(*tx_ring, eop);
 	}
 
-	tx_ring->next_to_clean = i;
+	/* Synchronize with E1000_DESC_UNUSED called from e1000_xmit_frame,
+	 * which will reuse the cleaned buffers.
+	 */
+	smp_store_release(&tx_ring->next_to_clean, i);
 
 	netdev_completed_queue(netdev, pkts_compl, bytes_compl);