Skip to contentSkip to conversation

libertas: Avoid reading past end of buffer

PATCH In review Kees Cook 2 participants 2 messages May 15, 2017 – May 24, 2017

Subsystems (3)
Networking Network drivers Marvell libertas wireless driver
lore
Share & tools
lore

Kees Cook

author
#0 lore raw

PATCH v3 1/1 libertas: 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, redefine the stat strings to be ETH_GSTRING_LEN sizes, like other drivers. This lets us use a single memcpy that does not leak rodata contents. Additionally adjust indentation to keep checkpatch.pl happy.

This was found with the future CONFIG_FORTIFY_SOURCE feature.

Cc Daniel Micay <[email protected]>
Signed-off-by Kees Cook <[email protected]>

---
v3:
- drop needless "*"; joe
- fix entry/exit in separate patch
v2:
- use ETH_GSTRING_LEN; joe

---
 drivers/net/wireless/marvell/libertas/mesh.c | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)
drivers/net/wireless/marvell/libertas/mesh.c +10 -16
index d0c881dd5846..2229fb448189 100644
@@ -1108,15 +1108,15 @@ void lbs_mesh_set_txpd(struct lbs_private *priv,
  * Ethtool related
  */
 
-static const char * const mesh_stat_strings[] = {
-			"drop_duplicate_bcast",
-			"drop_ttl_zero",
-			"drop_no_fwd_route",
-			"drop_no_buffers",
-			"fwded_unicast_cnt",
-			"fwded_bcast_cnt",
-			"drop_blind_table",
-			"tx_failed_cnt"
+static const char mesh_stat_strings[MESH_STATS_NUM][ETH_GSTRING_LEN] = {
+	"drop_duplicate_bcast",
+	"drop_ttl_zero",
+	"drop_no_fwd_route",
+	"drop_no_buffers",
+	"fwded_unicast_cnt",
+	"fwded_bcast_cnt",
+	"drop_blind_table",
+	"tx_failed_cnt"
 };
 
 void lbs_mesh_ethtool_get_stats(struct net_device *dev,

@@ -1170,17 +1170,11 @@ int lbs_mesh_ethtool_get_sset_count(struct net_device *dev, int sset)
 void lbs_mesh_ethtool_get_strings(struct net_device *dev,
 	uint32_t stringset, uint8_t *s)
 {
-	int i;
-
 	lbs_deb_enter(LBS_DEB_ETHTOOL);
 
 	switch (stringset) {
 	case ETH_SS_STATS:
-		for (i = 0; i < MESH_STATS_NUM; i++) {
-			memcpy(s + i * ETH_GSTRING_LEN,
-					mesh_stat_strings[i],
-					ETH_GSTRING_LEN);
-		}
+		memcpy(s, mesh_stat_strings, sizeof(mesh_stat_strings));
 		break;
 	}
 	lbs_deb_enter(LBS_DEB_ETHTOOL);
Signature · 6 lines
2.7.4


-- 
Kees Cook
Pixel Security
#1 lore raw
Quoted 11 lines · 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, redefine the stat strings to be ETH_GSTRING_LEN sizes, like other drivers. This lets us use a single memcpy that does not leak rodata contents. Additionally adjust indentation to keep checkpatch.pl happy.

This was found with the future CONFIG_FORTIFY_SOURCE feature.

Cc Daniel Micay <[email protected]>
Signed-off-by Kees Cook <[email protected]>

Patch applied to wireless-drivers-next.git, thanks.

12e3c0433e8a libertas: Avoid reading past end of buffer

Signature · 3 lines
https://patchwork.kernel.org/patch/9727997/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches