wifi: mac80211: Use struct instead of macro for PREP frame

The existing PREP_IE_* macros access HWMP PREP frame fields via hardcoded
byte offsets. When the AE (Address Extension) flag is set, an additional
6 bytes appear mid-frame, making the offset arithmetic error-prone.

Introduce typed packed C structs to represent the PREP frame layout:
  - ieee80211_mesh_hwmp_prep_top: fixed fields before the optional AE
    address
  - ieee80211_mesh_hwmp_prep_bottom: fields after the optional AE address

Add ieee80211_mesh_hwmp_prep_get_bottom() to locate the bottom struct
correctly based on whether the AE flag is set.

This preparatory refactoring is needed to fix a 2-byte overread of
orig_addr in hwmp_prep_frame_process() when AE is enabled, which is
addressed in a subsequent patch.

Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
Link: https://patch.msgid.link/20260529230952.124754-2-masashi.honma@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/include/linux/ieee80211-mesh.h b/include/linux/ieee80211-mesh.h
index bf4a544aed00572d4215e8f131c5b38c2b1cc25a..4ce4e47d6d0188b470339e34df83f157f48de4db 100644 (file)
--- a/include/linux/ieee80211-mesh.h
+++ b/include/linux/ieee80211-mesh.h
@@ -53,6 +53,24 @@ struct ieee80211_mesh_hwmp_preq_bottom {
        struct ieee80211_mesh_hwmp_preq_target targets[];
 } __packed;
 
+struct ieee80211_mesh_hwmp_prep_top {
+       u8 flags;
+       u8 hopcount;
+       u8 ttl;
+       u8 target_addr[ETH_ALEN];
+       __le32 target_sn;
+
+       /* optional Target External Address */
+       u8 variable[];
+} __packed;
+
+struct ieee80211_mesh_hwmp_prep_bottom {
+       __le32 lifetime;
+       __le32 metric;
+       u8 orig_addr[ETH_ALEN];
+       __le32 orig_sn;
+} __packed;
+
 /* Mesh flags */
 #define MESH_FLAGS_AE_A4       0x1
 #define MESH_FLAGS_AE_A5_A6    0x2
@@ -269,4 +287,13 @@ ieee80211_mesh_hwmp_preq_get_bottom(const u8 *ie)
                ieee80211_mesh_preq_prep_ae_enabled(ie) ? ETH_ALEN : 0];
 }
 
+static inline struct ieee80211_mesh_hwmp_prep_bottom *
+ieee80211_mesh_hwmp_prep_get_bottom(const u8 *ie)
+{
+       struct ieee80211_mesh_hwmp_prep_top *top = (void *)ie;
+
+       return (void *)&top->variable[
+               ieee80211_mesh_preq_prep_ae_enabled(ie) ? ETH_ALEN : 0];
+}
+
 #endif /* LINUX_IEEE80211_MESH_H */

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 1a6a22b185d9fe4a7a4126ebc1303729c5b892b2..39b782370df0a11e17ae6bca60d5af1e182b9e99 100644 (file)
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -37,16 +37,6 @@ static inline u16 u16_field_get(const u8 *preq_elem, int offset, bool ae)
 /* HWMP IE processing macros */
 #define AE_F_SET(x)            (*x & AE_F)
 
-#define PREP_IE_FLAGS(x)       (*(x))
-#define PREP_IE_HOPCOUNT(x)    (*(x + 1))
-#define PREP_IE_TTL(x)         (*(x + 2))
-#define PREP_IE_ORIG_ADDR(x)   (AE_F_SET(x) ? x + 27 : x + 21)
-#define PREP_IE_ORIG_SN(x)     u32_field_get(x, 27, AE_F_SET(x))
-#define PREP_IE_LIFETIME(x)    u32_field_get(x, 13, AE_F_SET(x))
-#define PREP_IE_METRIC(x)      u32_field_get(x, 17, AE_F_SET(x))
-#define PREP_IE_TARGET_ADDR(x) (x + 3)
-#define PREP_IE_TARGET_SN(x)   u32_field_get(x, 9, 0)
-
 #define PERR_IE_TTL(x)         (*(x))
 #define PERR_IE_TARGET_FLAGS(x)        (*(x + 2))
 #define PERR_IE_TARGET_ADDR(x) (x + 3)
@@ -419,11 +409,16 @@ static u32 hwmp_route_info_get(struct ieee80211_sub_if_data *sdata,
                 * so that we can easily use a single function to gather path
                 * information from both PREQ and PREP frames.
                 */
-               orig_addr = PREP_IE_TARGET_ADDR(hwmp_ie);
-               orig_sn = PREP_IE_TARGET_SN(hwmp_ie);
-               orig_lifetime = PREP_IE_LIFETIME(hwmp_ie);
-               orig_metric = PREP_IE_METRIC(hwmp_ie);
-               hopcount = PREP_IE_HOPCOUNT(hwmp_ie) + 1;
+               struct ieee80211_mesh_hwmp_prep_top *prep_elem_top =
+                       (void *)hwmp_ie;
+               struct ieee80211_mesh_hwmp_prep_bottom *prep_elem_bottom =
+                       ieee80211_mesh_hwmp_prep_get_bottom(hwmp_ie);
+
+               orig_addr = prep_elem_top->target_addr;
+               orig_sn = le32_to_cpu(prep_elem_top->target_sn);
+               orig_lifetime = le32_to_cpu(prep_elem_bottom->lifetime);
+               orig_metric = le32_to_cpu(prep_elem_bottom->metric);
+               hopcount = prep_elem_top->hopcount + 1;
                break;
        default:
                rcu_read_unlock();
@@ -714,6 +709,9 @@ static void hwmp_prep_frame_process(struct ieee80211_sub_if_data *sdata,
                                    const u8 *prep_elem, u32 metric)
 {
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+       struct ieee80211_mesh_hwmp_prep_top *prep_elem_top = (void *)prep_elem;
+       struct ieee80211_mesh_hwmp_prep_bottom *prep_elem_bottom =
+               ieee80211_mesh_hwmp_prep_get_bottom(prep_elem);
        struct mesh_path *mpath;
        const u8 *target_addr, *orig_addr;
        u8 ttl, hopcount, flags;
@@ -721,9 +719,9 @@ static void hwmp_prep_frame_process(struct ieee80211_sub_if_data *sdata,
        u32 target_sn, orig_sn, lifetime;
 
        mhwmp_dbg(sdata, "received PREP from %pM\n",
-                 PREP_IE_TARGET_ADDR(prep_elem));
+                 prep_elem_top->target_addr);
 
-       orig_addr = PREP_IE_ORIG_ADDR(prep_elem);
+       orig_addr = prep_elem_bottom->orig_addr;
        if (ether_addr_equal(orig_addr, sdata->vif.addr))
                /* destination, no forwarding required */
                return;
@@ -731,7 +729,7 @@ static void hwmp_prep_frame_process(struct ieee80211_sub_if_data *sdata,
        if (!ifmsh->mshcfg.dot11MeshForwarding)
                return;
 
-       ttl = PREP_IE_TTL(prep_elem);
+       ttl = prep_elem_top->ttl;
        if (ttl <= 1) {
                sdata->u.mesh.mshstats.dropped_frames_ttl++;
                return;
@@ -750,12 +748,12 @@ static void hwmp_prep_frame_process(struct ieee80211_sub_if_data *sdata,
        memcpy(next_hop, next_hop_deref_protected(mpath)->sta.addr, ETH_ALEN);
        spin_unlock_bh(&mpath->state_lock);
        --ttl;
-       flags = PREP_IE_FLAGS(prep_elem);
-       lifetime = PREP_IE_LIFETIME(prep_elem);
-       hopcount = PREP_IE_HOPCOUNT(prep_elem) + 1;
-       target_addr = PREP_IE_TARGET_ADDR(prep_elem);
-       target_sn = PREP_IE_TARGET_SN(prep_elem);
-       orig_sn = PREP_IE_ORIG_SN(prep_elem);
+       flags = prep_elem_top->flags;
+       lifetime = le32_to_cpu(prep_elem_bottom->lifetime);
+       hopcount = prep_elem_top->hopcount + 1;
+       target_addr = prep_elem_top->target_addr;
+       target_sn = le32_to_cpu(prep_elem_top->target_sn);
+       orig_sn = le32_to_cpu(prep_elem_bottom->orig_sn);
 
        mesh_path_sel_frame_tx(MPATH_PREP, flags, orig_addr, orig_sn, 0,
                               target_addr, target_sn, next_hop, hopcount,