[netdrvr] tulip_read_eeprom fixes for BUG 4420

If "location" is > "addr_len" bits, the high bits of location would interfere
with the READ_CMD sent to the eeprom controller.

A patch was submitted to bug:
    http://bugzilla.kernel.org/show_bug.cgi?id=4420

which simply truncated the "location", read whatever was in "location
modulo addr_len", and returned that value. That avoids confusing the
eeprom but seems like the wrong solution to me.

Correct would be to not read beyond "1 << addr_len" address of the eeprom.
I am submitting two changes to implement this:
1) tulip_read_eeprom will return zero (since we can't return -EINVAL)
   if this is attempted (defensive programming).
2) In tulip_core.c, fix the tulip_read_eeprom caller so they don't
   iterate past addr_len bits and make sure the entire tp->eeprom[]
   array is cleared.

I konw we don't strictly need both. I would prefer both in the tree
since it documents the issue and provides a second "defense" from
the bug from creeping back in.

Signed-off-by: Grant Grundler <grundler@parisc-linux.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

2 files changed, 12 insertions, 1 deletions

diff --git a/drivers/net/tulip/eeprom.c b/drivers/net/tulip/eeprom.c
index 206918bad539..da2206f6021d 100644
--- a/drivers/net/tulip/eeprom.c
+++ b/drivers/net/tulip/eeprom.c
@@ -343,6 +343,12 @@ int __devinit tulip_read_eeprom(struct net_device *dev, int location, int addr_l
         void __iomem *ee_addr = tp->base_addr + CSR9;
         int read_cmd = location | (EE_READ_CMD << addr_len);
 
+        /* If location is past the end of what we can address, don't
+         * read some other location (ie truncate). Just return zero.
+         */
+        if (location > (1 << addr_len) - 1)
+                return 0;
+
         iowrite32(EE_ENB & ~EE_CS, ee_addr);
         iowrite32(EE_ENB, ee_addr);
 
diff --git a/drivers/net/tulip/tulip_core.c b/drivers/net/tulip/tulip_core.c
index ed600bf56e78..82f404b76d81 100644
--- a/drivers/net/tulip/tulip_core.c
+++ b/drivers/net/tulip/tulip_core.c
@@ -1437,6 +1437,7 @@ static int __devinit tulip_init_one (struct pci_dev *pdev,
            EEPROM.
            */
         ee_data = tp->eeprom;
+        memset(ee_data, 0, sizeof(tp->eeprom));
         sum = 0;
         if (chip_idx == LC82C168) {
                 for (i = 0; i < 3; i++) {
@@ -1458,8 +1459,12 @@ static int __devinit tulip_init_one (struct pci_dev *pdev,
                 /* A serial EEPROM interface, we read now and sort it out later. */
                 int sa_offset = 0;
                 int ee_addr_size = tulip_read_eeprom(dev, 0xff, 8) & 0x40000 ? 8 : 6;
+                int ee_max_addr = ((1 << ee_addr_size) - 1) * sizeof(u16);
 
-                for (i = 0; i < sizeof(tp->eeprom); i+=2) {
+                if (ee_max_addr > sizeof(tp->eeprom))
+                        ee_max_addr = sizeof(tp->eeprom);
+
+                for (i = 0; i < ee_max_addr ; i += sizeof(u16)) {
                         u16 data = tulip_read_eeprom(dev, i/2, ee_addr_size);
                         ee_data[i] = data & 0xff;
                         ee_data[i + 1] = data >> 8;