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drivers, net, ethernet: convert mtk_eth.dma_refcnt from atomic_t to refcount_t 

atomic_t variables are currently used to implement reference
counters with the following properties:
 - counter is initialized to 1 using atomic_set()
 - a resource is freed upon counter reaching zero
 - once counter reaches zero, its further
   increments aren't allowed
 - counter schema uses basic atomic operations
   (set, inc, inc_not_zero, dec_and_test, etc.)

Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.

The variable mtk_eth.dma_refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Elena Reshetova 2017-10-20 10:23:36 +03:00 committed by David S. Miller
parent eaf6ab7643
commit c6d4e63e06
2 changed files with 8 additions and 4 deletions
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8
drivers/net/ethernet/mediatek/mtk_eth_soc.c
View File

@ -1817,7 +1817,7 @@ static int mtk_open(struct net_device *dev)
struct mtk_eth *eth = mac->hw;
/* we run 2 netdevs on the same dma ring so we only bring it up once */
if (!atomic_read(&eth->dma_refcnt)) {
if (!refcount_read(&eth->dma_refcnt)) {
int err = mtk_start_dma(eth);
if (err)
@ -1827,8 +1827,10 @@ static int mtk_open(struct net_device *dev)
napi_enable(&eth->rx_napi);
mtk_tx_irq_enable(eth, MTK_TX_DONE_INT);
mtk_rx_irq_enable(eth, MTK_RX_DONE_INT);
refcount_set(&eth->dma_refcnt, 1);
}
atomic_inc(&eth->dma_refcnt);
else
refcount_inc(&eth->dma_refcnt);
phy_start(dev->phydev);
netif_start_queue(dev);
@ -1868,7 +1870,7 @@ static int mtk_stop(struct net_device *dev)
phy_stop(dev->phydev);
/* only shutdown DMA if this is the last user */
if (!atomic_dec_and_test(&eth->dma_refcnt))
if (!refcount_dec_and_test(&eth->dma_refcnt))
return 0;
mtk_tx_irq_disable(eth, MTK_TX_DONE_INT);

4
drivers/net/ethernet/mediatek/mtk_eth_soc.h
View File

@ -15,6 +15,8 @@
#ifndef MTK_ETH_H
#define MTK_ETH_H
#include <linux/refcount.h>
#define MTK_QDMA_PAGE_SIZE 2048
#define MTK_MAX_RX_LENGTH 1536
#define MTK_TX_DMA_BUF_LEN 0x3fff
@ -632,7 +634,7 @@ struct mtk_eth {
struct regmap *pctl;
u32 chip_id;
bool hwlro;
atomic_t dma_refcnt;
refcount_t dma_refcnt;
struct mtk_tx_ring tx_ring;
struct mtk_rx_ring rx_ring[MTK_MAX_RX_RING_NUM];
struct mtk_rx_ring rx_ring_qdma;