[PATCH 3/3] 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.

Assisted-by: Claude:Sonnet 4.6
Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
---
 include/linux/ieee80211-mesh.h | 38 ++++++++++++++++++++++++++++++++++
 net/mac80211/mesh_hwmp.c       | 11 ++++++++--
 net/mac80211/parse.c           |  9 ++++++--
 3 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/include/linux/ieee80211-mesh.h b/include/linux/ieee80211-mesh.h
index ddbf475c1cc8..1bca65e49309 100644
--- a/include/linux/ieee80211-mesh.h
+++ b/include/linux/ieee80211-mesh.h
@@ -61,6 +61,7 @@ struct ieee80211s_hdr {
 #define PREP_IE_TARGET_SN(x)	u32_field_get(x, 9, 0)
 
 #define PERR_IE_TTL(x)			(*(x))
+#define PERR_IE_NUMBER_OF_DST(x)	(*(x + 1))
 #define PERR_IE_TARGET_FLAGS(x)		(*(x + 2))
 #define PERR_IE_TARGET_ADDR(x)		(x + 3)
 #define PERR_IE_TARGET_SN(x)		u32_field_get(x, 9, 0)
@@ -301,4 +302,41 @@ static inline bool ieee80211_mesh_prep_size_ok(const u8 *pos, u8 elen)
 	return true;
 }
 
+/* IEEE Std 802.11-2016 9.4.2.115 PERR element */
+static inline bool ieee80211_mesh_perr_size_ok(const u8 *pos, u8 elen)
+{
+	u8 number_of_dst;
+	u8 needed;
+	const u8 *start;
+	int i;
+
+	number_of_dst = PERR_IE_NUMBER_OF_DST(pos);
+	if (number_of_dst < 1 || number_of_dst > 19)
+		return false;
+
+	start = pos;
+	needed = 1 /* Element TTL */ + 1 /* Number of Destinations */;
+	pos += 2;
+
+	for (i = 0; i < number_of_dst; i++) {
+		u8 dst_len;
+
+		if (pos - start >= elen)
+			return false;
+
+		dst_len = 1 /* Flags */ + 6 /* Destination Address */ +
+			  4 /* HWMP Sequence Number */ +
+			  (AE_F_SET(pos) ? 6 : 0)
+			  /* Destination External Address */ +
+			  2 /* Reason Code */;
+		needed += dst_len;
+		pos += dst_len;
+	}
+
+	if (elen != needed)
+		return false;
+
+	return true;
+}
+
 #endif /* LINUX_IEEE80211_MESH_H */
diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index c70cfc2d6299..d2295aa54bb4 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -902,6 +902,7 @@ void mesh_rx_path_sel_frame(struct ieee80211_sub_if_data *sdata,
 	u32 path_metric;
 	struct sta_info *sta;
 	u8 target_count;
+	u8 number_of_dst;
 
 	/* need action_code */
 	if (len < IEEE80211_MIN_ACTION_SIZE(mesh_action))
@@ -952,9 +953,15 @@ 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 */
+		/* Right now we support only one destination per PERR */
+		number_of_dst = PERR_IE_NUMBER_OF_DST(elems->perr);
+		if (number_of_dst != 1)
 			goto free;
+
+		/* Right now we do not support AE (Address Extension) */
+		if (PERR_IE_TARGET_FLAGS(elems->perr) & 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