Re: [PATCH] e1000e: fix heap overflow in e1000_set_eeprom()

The ETHTOOL_SETEEPROM ioctl copies user data into a kmalloc'ed buffer
without validating eeprom->len and eeprom->offset. A CAP_NET_ADMIN
user can overflow the heap and crash the kernel or gain code execution.

Validate length and offset before kmalloc() to avoid leaking eeprom_buff.

Fixes: bc7f75fa9788 ("[E1000E]: New pci-express e1000 driver (currently for ICH9 devices only)")
Reported-by: Mikael Wessel <redacted>
Signed-off-by: Mikael Wessel <redacted>
Cc: stable@vger.kernel.org
---
  drivers/net/ethernet/intel/e1000e/ethtool.c | 9 +++++----
  1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/ethtool.c b/drivers/net/ethernet/intel/e1000e/ethtool.c
index 98e541e39730..d04e59528619 100644
--- a/drivers/net/ethernet/intel/e1000e/ethtool.c
+++ b/drivers/net/ethernet/intel/e1000e/ethtool.c

@@ -561,7 +561,7 @@ static int e1000_set_eeprom(struct net_device *netdev,
  		return -EOPNOTSUPP;
  
  	if (eeprom->magic !=
-	    (adapter->pdev->vendor | (adapter->pdev->device << 16)))
+		(adapter->pdev->vendor | (adapter->pdev->device << 16)))

  		return -EFAULT;
  
  	if (adapter->flags & FLAG_READ_ONLY_NVM)

@@ -569,6 +569,10 @@ static int e1000_set_eeprom(struct net_device *netdev,
  
  	max_len = hw->nvm.word_size * 2;
  
+	/* bounds check: offset + len must not exceed EEPROM size */
+	if (eeprom->offset + eeprom->len > max_len)
+		return -EINVAL;
+
  	first_word = eeprom->offset >> 1;
  	last_word = (eeprom->offset + eeprom->len - 1) >> 1;
  	eeprom_buff = kmalloc(max_len, GFP_KERNEL);

@@ -596,9 +600,6 @@ static int e1000_set_eeprom(struct net_device *netdev,
  	for (i = 0; i < last_word - first_word + 1; i++)
  		le16_to_cpus(&eeprom_buff[i]);
  
-        if (eeprom->len > max_len ||
-            eeprom->offset > max_len - eeprom->len)
-                return -EINVAL;