linux-kernel - [PATCH] bna: ethtool: Avoid reading past end of buffer

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Date:   Fri, 5 May 2017 15:30:23 -0700
From:   Kees Cook <keescook@...omium.org>
To:     netdev@...r.kernel.org
Cc:     Rasesh Mody <rasesh.mody@...ium.com>,
        Sudarsana Kalluru <sudarsana.kalluru@...ium.com>,
        linux-kernel@...r.kernel.org, Dept-GELinuxNICDev@...ium.com,
        Daniel Micay <danielmicay@...il.com>
Subject: [PATCH] bna: ethtool: Avoid reading past end of buffer

Using memcpy() from a string that is shorter than the length copied means
the destination buffer is being filled with arbitrary data from the kernel
rodata segment. Instead, use strncpy() which will fill the trailing bytes
with zeros.

This was found with the future CONFIG_FORTIFY_SOURCE feature.

Cc: Daniel Micay <danielmicay@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/net/ethernet/brocade/bna/bnad_ethtool.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/brocade/bna/bnad_ethtool.c b/drivers/net/ethernet/brocade/bna/bnad_ethtool.c
index 286593922139..31032de5843b 100644
--- a/drivers/net/ethernet/brocade/bna/bnad_ethtool.c
+++ b/drivers/net/ethernet/brocade/bna/bnad_ethtool.c
@@ -547,8 +547,8 @@ bnad_get_strings(struct net_device *netdev, u32 stringset, u8 *string)
 		for (i = 0; i < BNAD_ETHTOOL_STATS_NUM; i++) {
 			BUG_ON(!(strlen(bnad_net_stats_strings[i]) <
 				   ETH_GSTRING_LEN));
-			memcpy(string, bnad_net_stats_strings[i],
-			       ETH_GSTRING_LEN);
+			strncpy(string, bnad_net_stats_strings[i],
+				ETH_GSTRING_LEN);
 			string += ETH_GSTRING_LEN;
 		}
 		bmap = bna_tx_rid_mask(&bnad->bna);
-- 
2.7.4


-- 
Kees Cook
Pixel Security