From c6d4e63e065e796d2f2734c1e4e13f85f1c1c5e4 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 10:23:36 +0300 Subject: 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 Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: David S. Miller --- drivers/net/ethernet/mediatek/mtk_eth_soc.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'drivers/net/ethernet/mediatek/mtk_eth_soc.c') diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c index 5e81a7263654..54adfd967858 100644 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c @@ -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(ð->dma_refcnt)) { + if (!refcount_read(ð->dma_refcnt)) { int err = mtk_start_dma(eth); if (err) @@ -1827,8 +1827,10 @@ static int mtk_open(struct net_device *dev) napi_enable(ð->rx_napi); mtk_tx_irq_enable(eth, MTK_TX_DONE_INT); mtk_rx_irq_enable(eth, MTK_RX_DONE_INT); + refcount_set(ð->dma_refcnt, 1); } - atomic_inc(ð->dma_refcnt); + else + refcount_inc(ð->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(ð->dma_refcnt)) + if (!refcount_dec_and_test(ð->dma_refcnt)) return 0; mtk_tx_irq_disable(eth, MTK_TX_DONE_INT); -- cgit v1.2.3