From faac9c4b753f420c02bdce0785d2657087830a12 Mon Sep 17 00:00:00 2001 From: Michael Chan Date: Thu, 14 Dec 2006 15:56:32 -0800 Subject: [PATCH] [BNX2]: Fix panic in bnx2_tx_int(). There was an off-by-one bug in bnx2_tx_avail(). If the tx ring is completely full, the producer and consumer indices may be apart by 256 even though the ring size is only 255. One entry in the ring is unused and must be properly accounted for when calculating the number of available entries. The bug caused the tx ring entries to be reused by mistake, overwriting active entries, and ultimately causing it to crash. This bug rarely occurs because the tx ring is rarely completely full. We always stop when there is less than MAX_SKB_FRAGS entries available in the ring. Thanks to Corey Kovacs and Andy Gospodarek for reporting the problem and helping to collect debug information. Signed-off-by: Michael Chan Signed-off-by: David S. Miller --- drivers/net/bnx2.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/drivers/net/bnx2.c b/drivers/net/bnx2.c index 7d824cf8ee2..f296c37f29b 100644 --- a/drivers/net/bnx2.c +++ b/drivers/net/bnx2.c @@ -217,9 +217,16 @@ static inline u32 bnx2_tx_avail(struct bnx2 *bp) u32 diff; smp_mb(); - diff = TX_RING_IDX(bp->tx_prod) - TX_RING_IDX(bp->tx_cons); - if (diff > MAX_TX_DESC_CNT) - diff = (diff & MAX_TX_DESC_CNT) - 1; + + /* The ring uses 256 indices for 255 entries, one of them + * needs to be skipped. + */ + diff = bp->tx_prod - bp->tx_cons; + if (unlikely(diff >= TX_DESC_CNT)) { + diff &= 0xffff; + if (diff == TX_DESC_CNT) + diff = MAX_TX_DESC_CNT; + } return (bp->tx_ring_size - diff); } -- 2.20.1