netdev - [PATCH] net: ethernet: dec: tulip: de4x5: fix possible array overflows in type3

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Date:   Wed, 17 Nov 2021 11:37:38 +0800
From:   Teng Qi <starmiku1207184332@...il.com>
To:     davem@...emloft.net, kuba@...nel.org, arnd@...db.de,
        tanghui20@...wei.com
Cc:     netdev@...r.kernel.org, linux-parisc@...r.kernel.org,
        linux-kernel@...r.kernel.org, baijiaju1990@...il.com,
        islituo@...il.com, Teng Qi <starmiku1207184332@...il.com>,
        TOTE Robot <oslab@...nghua.edu.cn>
Subject: [PATCH] net: ethernet: dec: tulip: de4x5: fix possible array overflows in type3_infoblock()

The definition of macro MOTO_SROM_BUG is:
  #define MOTO_SROM_BUG    (lp->active == 8 && (get_unaligned_le32(
  dev->dev_addr) & 0x00ffffff) == 0x3e0008)

and the if statement
  if (MOTO_SROM_BUG) lp->active = 0;

using this macro indicates lp->active could be 8. If lp->active is 8 and 
the second comparison of this macro is false. lp->active will remain 8 in:
  lp->phy[lp->active].gep = (*p ? p : NULL); p += (2 * (*p) + 1);
  lp->phy[lp->active].rst = (*p ? p : NULL); p += (2 * (*p) + 1);
  lp->phy[lp->active].mc  = get_unaligned_le16(p); p += 2;
  lp->phy[lp->active].ana = get_unaligned_le16(p); p += 2;
  lp->phy[lp->active].fdx = get_unaligned_le16(p); p += 2;
  lp->phy[lp->active].ttm = get_unaligned_le16(p); p += 2;
  lp->phy[lp->active].mci = *p;

However, the length of array lp->phy is 8, so array overflows can occur.
To fix these possible array overflows, we first check lp->active and then
set it to 0 if it is equal to DE4X5_MAX_PHY (i.e., 8).

Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
Signed-off-by: Teng Qi <starmiku1207184332@...il.com>
---
 drivers/net/ethernet/dec/tulip/de4x5.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/dec/tulip/de4x5.c b/drivers/net/ethernet/dec/tulip/de4x5.c
index 13121c4dcfe6..18132deac2bf 100644
--- a/drivers/net/ethernet/dec/tulip/de4x5.c
+++ b/drivers/net/ethernet/dec/tulip/de4x5.c
@@ -4708,7 +4708,8 @@ type3_infoblock(struct net_device *dev, u_char count, u_char *p)
     if (lp->state == INITIALISED) {
         lp->ibn = 3;
         lp->active = *p++;
-	if (MOTO_SROM_BUG) lp->active = 0;
+	/* The DE4X5_MAX_PHY is length of lp->phy, and its value is 8 */
+	if (MOTO_SROM_BUG || lp->active == DE4X5_MAX_PHY) lp->active = 0;
 	lp->phy[lp->active].gep = (*p ? p : NULL); p += (2 * (*p) + 1);
 	lp->phy[lp->active].rst = (*p ? p : NULL); p += (2 * (*p) + 1);
 	lp->phy[lp->active].mc  = get_unaligned_le16(p); p += 2;
-- 
2.25.1