[PATCH v8 6/6] wifi: mac80211: Fix PERR frame processing

[Masashi Honma <masashi.honma@gmail.com>]

There are no issues with the PERR processing itself; however, to maintain
consistency with the previous PREQ/PREP code modifications, I will create a
new mesh_path_parse_error_frame() function to separately implement the
frame format validation and the "not supported" check.

Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
---
 include/linux/ieee80211-mesh.h | 41 ++++++++++++++++++++++++++++++++++
 net/mac80211/mesh_hwmp.c       | 14 ++++++++++--
 net/mac80211/parse.c           |  9 ++++++--
 3 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/include/linux/ieee80211-mesh.h b/include/linux/ieee80211-mesh.h
index b4fca2937de0..bd83c647a578 100644
--- a/include/linux/ieee80211-mesh.h
+++ b/include/linux/ieee80211-mesh.h
@@ -365,4 +365,45 @@ static inline bool ieee80211_mesh_prep_size_ok(const u8 *pos, u8 elen)
 	return elen == needed;
 }
 
+/* IEEE Std 802.11-2016 9.4.2.115 PERR element */
+static inline bool ieee80211_mesh_perr_size_ok(const u8 *pos, u8 elen)
+{
+	struct ieee80211_mesh_hwmp_perr *perr_elem = (void *)pos;
+	u8 number_of_dst;
+	u8 needed;
+	const u8 *start;
+	int i;
+
+	start = pos;
+	needed = sizeof(struct ieee80211_mesh_hwmp_perr);
+	pos += sizeof(struct ieee80211_mesh_hwmp_perr);
+
+	/* Check if the element contains number of dst */
+	if (elen < needed)
+		return false;
+
+	number_of_dst = perr_elem->number_of_dst;
+	if (number_of_dst < 1 || number_of_dst > 19)
+		return false;
+
+	for (i = 0; i < number_of_dst; i++) {
+		struct ieee80211_mesh_hwmp_perr_dst *perr_dst =
+			&perr_elem->dsts[i];
+		u8 dst_len;
+
+		/* Check if the element contains flags */
+		if (elen < pos - start + 1)
+			return false;
+
+		dst_len = sizeof(struct ieee80211_mesh_hwmp_perr_dst) +
+			  ((perr_dst->flags & AE_F) ? ETH_ALEN : 0)
+			  /* Destination External Address */ +
+			  2 /* Reason Code */;
+		needed += dst_len;
+		pos += dst_len;
+	}
+
+	return elen == needed;
+}
+
 #endif /* LINUX_IEEE80211_MESH_H */
diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 391d37721b23..a74d7b28a35d 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -957,9 +957,19 @@ void mesh_rx_path_sel_frame(struct ieee80211_sub_if_data *sdata,
 						path_metric);
 	}
 	if (elems->perr) {
-		if (elems->perr_len != 15)
-			/* Right now we support only one destination per PERR */
+		struct ieee80211_mesh_hwmp_perr *perr_elem =
+			(struct ieee80211_mesh_hwmp_perr *)elems->perr;
+		int i;
+
+		/* Right now we support only one destination per PERR */
+		if (perr_elem->number_of_dst != 1)
 			goto free;
+
+		/* Right now we do not support AE (Address Extension) */
+		for (i = 0; i < perr_elem->number_of_dst; i++)
+			if (perr_elem->dsts[i].flags & AE_F)
+				goto free;
+
 		hwmp_perr_frame_process(sdata, mgmt, elems->perr);
 	}
 	if (elems->rann)
diff --git a/net/mac80211/parse.c b/net/mac80211/parse.c
index bbd1e1bc77b4..d84e5e12ad24 100644
--- a/net/mac80211/parse.c
+++ b/net/mac80211/parse.c
@@ -565,8 +565,13 @@ _ieee802_11_parse_elems_full(struct ieee80211_elems_parse_params *params,
 			}
 			break;
 		case WLAN_EID_PERR:
-			elems->perr = pos;
-			elems->perr_len = elen;
+			if (ieee80211_mesh_perr_size_ok(pos, elen)) {
+				elems->perr = pos;
+				elems->perr_len = elen;
+			} else {
+				elem_parse_failed =
+					IEEE80211_PARSE_ERR_BAD_ELEM_SIZE;
+			}
 			break;
 		case WLAN_EID_RANN:
 			if (elen >= sizeof(struct ieee80211_rann_ie))
-- 
2.43.0