Subject: [PATCH] Re: Error handling corner case found during audits

From: "Kok, Auke" <[email-masked]>
Date: Tue, 29 Apr 2008 11:18:55 -0700

Alan Cox wrote:
> Not sure what should happen here.
> 
> 
> diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.25-mm1/drivers/net/e1000e/ethtool.c linux-2.6.25-mm1/drivers/net/e1000e/ethtool.c
> --- linux.vanilla-2.6.25-mm1/drivers/net/e1000e/ethtool.c	2008-04-28 11:36:49.000000000 +0100
> +++ linux-2.6.25-mm1/drivers/net/e1000e/ethtool.c	2008-04-18 16:42:41.000000000 +0100
> @@ -494,6 +494,8 @@
>  		for (i = 0; i < last_word - first_word + 1; i++) {
>  			ret_val = e1000_read_nvm(hw, first_word + i, 1,
>  						      &eeprom_buff[i]);
> +			/* ERROR: This path leaves eeprom_buf containing
> +			   old kernel bytes we then byteswap/return */
>  			if (ret_val)
>  				break;
>  		}

either we fill the buffer with 0xff (the determined value for "empty eeprom"), or
just kzalloc the buffer instead. This should be enough of a warning for the user
that something is really wrong.

Auke

---

e1000e: don't return half-read eeprom on error

On a read error, e1000e might have returned uninitialized block of eeprom data
back to userspace. The convention is that 0xff is "empty", so mark the entire
eeprom as empty in case of an error.

Signed-off-by: Auke Kok <[email-masked]>

---
diff --git a/drivers/net/e1000e/ethtool.c b/drivers/net/e1000e/ethtool.c
index b1b784a..8b04a42 100644
--- a/drivers/net/e1000e/ethtool.c
+++ b/drivers/net/e1000e/ethtool.c
@@ -510,8 +510,12 @@ static int e1000_get_eeprom(struct net_device *netdev,
 		for (i = 0; i < last_word - first_word + 1; i++) {
 			ret_val = e1000_read_nvm(hw, first_word + i, 1,
 						      &eeprom_buff[i]);
-			if (ret_val)
+			if (ret_val) {
+				/* a read error occurred, throw away the
+				 * result */
+				memset(eeprom_buff, 0xff, sizeof(eeprom_buff));
 				break;
+			}
 		}
 	}