igb: fix bit_shift to be in [1..8] range

[ Upstream commit 60d758659f1fb49e0d5b6ac2691ede8c0958795b ]

In igb_hash_mc_addr() the expression:
        "mc_addr[4] >> 8 - bit_shift", right shifting "mc_addr[4]"
shift by more than 7 bits always yields zero, so hash becomes not so different.
Add initialization with bit_shift = 1 and add a loop condition to ensure
bit_shift will be always in [1..8] range.

Fixes: d49a2a41710f ("igb: PCI-Express 82575 Gigabit Ethernet driver")
Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/ethernet/intel/igb/e1000_mac.c b/drivers/net/ethernet/intel/igb/e1000_mac.c
index 79ee0a7472608ec823e29d576a40a29b05237fe1..4e69cb2c025fd3459b6574229948e15ac35785b7 100644 (file)
--- a/drivers/net/ethernet/intel/igb/e1000_mac.c
+++ b/drivers/net/ethernet/intel/igb/e1000_mac.c
@@ -425,7 +425,7 @@ void igb_mta_set(struct e1000_hw *hw, u32 hash_value)
 static u32 igb_hash_mc_addr(struct e1000_hw *hw, u8 *mc_addr)
 {
        u32 hash_value, hash_mask;
-       u8 bit_shift = 0;
+       u8 bit_shift = 1;
 
        /* Register count multiplied by bits per register */
        hash_mask = (hw->mac.mta_reg_count * 32) - 1;
@@ -433,7 +433,7 @@ static u32 igb_hash_mc_addr(struct e1000_hw *hw, u8 *mc_addr)
        /* For a mc_filter_type of 0, bit_shift is the number of left-shifts
         * where 0xFF would still fall within the hash mask.
         */
-       while (hash_mask >> bit_shift != 0xFF)
+       while (hash_mask >> bit_shift != 0xFF && bit_shift < 4)
                bit_shift++;
 
        /* The portion of the address that is used for the hash table