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

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

[Kees Cook]

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@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.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

Re: [PATCH] bna: ethtool: Avoid reading past end of buffer

[David Miller]

From: Kees Cook <keescook@chromium.org>
Date: Fri, 5 May 2017 15:30:23 -0700

> 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@gmail.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Applied.