Date: Tue,  2 Apr 2024 19:23:01 +0200
From: Erick Archer <erick.archer@...look.com>
To: Marek Lindner <mareklindner@...mailbox.ch>,
	Simon Wunderlich <sw@...onwunderlich.de>,
	Antonio Quartulli <a@...table.cc>,
	Sven Eckelmann <sven@...fation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Erick Archer <erick.archer@...look.com>,
	b.a.t.m.a.n@...ts.open-mesh.org,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] batman-adv: Add flex array to struct batadv_tvlv_tt_data

The "struct batadv_tvlv_tt_data" uses a dynamically sized set of
trailing elements. Specifically, it uses an array of structures of type
"batadv_tvlv_tt_vlan_data". So, use the preferred way in the kernel
declaring a flexible array [1].

The order in which the structure batadv_tvlv_tt_data and the structure
batadv_tvlv_tt_vlan_data are defined must be swap to avoid an incomplete
type error.

Also, avoid the open-coded arithmetic in memory allocator functions [2]
using the "struct_size" macro and use the "flex_array_size" helper to
clarify some calculations, when possible.

Moreover, the new structure member also allow us to avoid the open-coded
arithmetic on pointers in some situations. Take advantage of this.

This code was detected with the help of Coccinelle, and audited and
modified manually.

Link: https://www.kernel.org/doc/html/next/process/deprecated.html#zero-length-and-one-element-arrays [1]
Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [2]
Signed-off-by: Erick Archer <erick.archer@...look.com>
---
Hi,

I would like to add the "__counted_by(num_vlan)" tag to the new flex member
but I don't know if this line can affect it.

ntohs(tt_data->num_vlan)

If there is no problem I can send a v2 with the "__counted_by" tag.

The Coccinelle script used to detect this code pattern is the following:

virtual report

@rule1@
type t1;
type t2;
identifier i0;
identifier i1;
identifier i2;
identifier ALLOC =~ "kmalloc|kzalloc|kmalloc_node|kzalloc_node|vmalloc|vzalloc|kvmalloc|kvzalloc";
position p1;
@@

i0 = sizeof(t1) + sizeof(t2) * i1;
...
i2 = ALLOC@p1(..., i0, ...);

@script:python depends on report@
p1 << rule1.p1;
@@

msg = "WARNING: verify allocation on line %s" % (p1[0].line)
coccilib.report.print_report(p1[0],msg)

Regards,
Erick
---
 include/uapi/linux/batadv_packet.h | 28 +++++++++---------
 net/batman-adv/translation-table.c | 47 ++++++++++++------------------
 2 files changed, 33 insertions(+), 42 deletions(-)

diff --git a/include/uapi/linux/batadv_packet.h b/include/uapi/linux/batadv_packet.h
index 6e25753015df..49cd345b84a7 100644
--- a/include/uapi/linux/batadv_packet.h
+++ b/include/uapi/linux/batadv_packet.h
@@ -592,19 +592,6 @@ struct batadv_tvlv_gateway_data {
 	__be32 bandwidth_up;
 };
 
-/**
- * struct batadv_tvlv_tt_data - tt data propagated through the tt tvlv container
- * @flags: translation table flags (see batadv_tt_data_flags)
- * @ttvn: translation table version number
- * @num_vlan: number of announced VLANs. In the TVLV this struct is followed by
- *  one batadv_tvlv_tt_vlan_data object per announced vlan
- */
-struct batadv_tvlv_tt_data {
-	__u8   flags;
-	__u8   ttvn;
-	__be16 num_vlan;
-};
-
 /**
  * struct batadv_tvlv_tt_vlan_data - vlan specific tt data propagated through
  *  the tt tvlv container
@@ -618,6 +605,21 @@ struct batadv_tvlv_tt_vlan_data {
 	__u16  reserved;
 };
 
+/**
+ * struct batadv_tvlv_tt_data - tt data propagated through the tt tvlv container
+ * @flags: translation table flags (see batadv_tt_data_flags)
+ * @ttvn: translation table version number
+ * @num_vlan: number of announced VLANs. In the TVLV this struct is followed by
+ *  one batadv_tvlv_tt_vlan_data object per announced vlan
+ * @vlan_data: array of batadv_tvlv_tt_vlan_data objects
+ */
+struct batadv_tvlv_tt_data {
+	__u8   flags;
+	__u8   ttvn;
+	__be16 num_vlan;
+	struct batadv_tvlv_tt_vlan_data vlan_data[];
+};
+
 /**
  * struct batadv_tvlv_tt_change - translation table diff data
  * @flags: status indicators concerning the non-mesh client (see
diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index b95c36765d04..96d22d8209f4 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -856,8 +856,7 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 		num_entries += atomic_read(&vlan->tt.num_entries);
 	}
 
-	change_offset = sizeof(**tt_data);
-	change_offset += num_vlan * sizeof(*tt_vlan);
+	change_offset = struct_size(*tt_data, vlan_data, num_vlan);
 
 	/* if tt_len is negative, allocate the space needed by the full table */
 	if (*tt_len < 0)
@@ -876,7 +875,7 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 	(*tt_data)->ttvn = atomic_read(&orig_node->last_ttvn);
 	(*tt_data)->num_vlan = htons(num_vlan);
 
-	tt_vlan = (struct batadv_tvlv_tt_vlan_data *)(*tt_data + 1);
+	tt_vlan = (*tt_data)->vlan_data;
 	hlist_for_each_entry(vlan, &orig_node->vlan_list, list) {
 		tt_vlan->vid = htons(vlan->vid);
 		tt_vlan->crc = htonl(vlan->tt.crc);
@@ -936,8 +935,7 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 		total_entries += vlan_entries;
 	}
 
-	change_offset = sizeof(**tt_data);
-	change_offset += num_vlan * sizeof(*tt_vlan);
+	change_offset = struct_size(*tt_data, vlan_data, num_vlan);
 
 	/* if tt_len is negative, allocate the space needed by the full table */
 	if (*tt_len < 0)
@@ -956,7 +954,7 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 	(*tt_data)->ttvn = atomic_read(&bat_priv->tt.vn);
 	(*tt_data)->num_vlan = htons(num_vlan);
 
-	tt_vlan = (struct batadv_tvlv_tt_vlan_data *)(*tt_data + 1);
+	tt_vlan = (*tt_data)->vlan_data;
 	hlist_for_each_entry(vlan, &bat_priv->softif_vlan_list, list) {
 		vlan_entries = atomic_read(&vlan->tt.num_entries);
 		if (vlan_entries < 1)
@@ -2916,7 +2914,6 @@ static bool batadv_send_tt_request(struct batadv_priv *bat_priv,
 {
 	struct batadv_tvlv_tt_data *tvlv_tt_data = NULL;
 	struct batadv_tt_req_node *tt_req_node = NULL;
-	struct batadv_tvlv_tt_vlan_data *tt_vlan_req;
 	struct batadv_hard_iface *primary_if;
 	bool ret = false;
 	int i, size;
@@ -2932,7 +2929,7 @@ static bool batadv_send_tt_request(struct batadv_priv *bat_priv,
 	if (!tt_req_node)
 		goto out;
 
-	size = sizeof(*tvlv_tt_data) + sizeof(*tt_vlan_req) * num_vlan;
+	size = struct_size(tvlv_tt_data, vlan_data, num_vlan);
 	tvlv_tt_data = kzalloc(size, GFP_ATOMIC);
 	if (!tvlv_tt_data)
 		goto out;
@@ -2944,12 +2941,10 @@ static bool batadv_send_tt_request(struct batadv_priv *bat_priv,
 	/* send all the CRCs within the request. This is needed by intermediate
 	 * nodes to ensure they have the correct table before replying
 	 */
-	tt_vlan_req = (struct batadv_tvlv_tt_vlan_data *)(tvlv_tt_data + 1);
 	for (i = 0; i < num_vlan; i++) {
-		tt_vlan_req->vid = tt_vlan->vid;
-		tt_vlan_req->crc = tt_vlan->crc;
+		tvlv_tt_data->vlan_data[i].vid = tt_vlan->vid;
+		tvlv_tt_data->vlan_data[i].crc = tt_vlan->crc;
 
-		tt_vlan_req++;
 		tt_vlan++;
 	}
 
@@ -3001,7 +2996,6 @@ static bool batadv_send_other_tt_response(struct batadv_priv *bat_priv,
 	struct batadv_orig_node *res_dst_orig_node = NULL;
 	struct batadv_tvlv_tt_change *tt_change;
 	struct batadv_tvlv_tt_data *tvlv_tt_data = NULL;
-	struct batadv_tvlv_tt_vlan_data *tt_vlan;
 	bool ret = false, full_table;
 	u8 orig_ttvn, req_ttvn;
 	u16 tvlv_len;
@@ -3024,10 +3018,9 @@ static bool batadv_send_other_tt_response(struct batadv_priv *bat_priv,
 	orig_ttvn = (u8)atomic_read(&req_dst_orig_node->last_ttvn);
 	req_ttvn = tt_data->ttvn;
 
-	tt_vlan = (struct batadv_tvlv_tt_vlan_data *)(tt_data + 1);
 	/* this node doesn't have the requested data */
 	if (orig_ttvn != req_ttvn ||
-	    !batadv_tt_global_check_crc(req_dst_orig_node, tt_vlan,
+	    !batadv_tt_global_check_crc(req_dst_orig_node, tt_data->vlan_data,
 					ntohs(tt_data->num_vlan)))
 		goto out;
 
@@ -3370,7 +3363,6 @@ static void batadv_handle_tt_response(struct batadv_priv *bat_priv,
 	struct batadv_orig_node *orig_node = NULL;
 	struct batadv_tvlv_tt_change *tt_change;
 	u8 *tvlv_ptr = (u8 *)tt_data;
-	u16 change_offset;
 
 	batadv_dbg(BATADV_DBG_TT, bat_priv,
 		   "Received TT_RESPONSE from %pM for ttvn %d t_size: %d [%c]\n",
@@ -3383,10 +3375,7 @@ static void batadv_handle_tt_response(struct batadv_priv *bat_priv,
 
 	spin_lock_bh(&orig_node->tt_lock);
 
-	change_offset = sizeof(struct batadv_tvlv_tt_vlan_data);
-	change_offset *= ntohs(tt_data->num_vlan);
-	change_offset += sizeof(*tt_data);
-	tvlv_ptr += change_offset;
+	tvlv_ptr += struct_size(tt_data, vlan_data, ntohs(tt_data->num_vlan));
 
 	tt_change = (struct batadv_tvlv_tt_change *)tvlv_ptr;
 	if (tt_data->flags & BATADV_TT_FULL_TABLE) {
@@ -3985,10 +3974,10 @@ static void batadv_tt_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
 					  u8 flags, void *tvlv_value,
 					  u16 tvlv_value_len)
 {
-	struct batadv_tvlv_tt_vlan_data *tt_vlan;
 	struct batadv_tvlv_tt_change *tt_change;
 	struct batadv_tvlv_tt_data *tt_data;
 	u16 num_entries, num_vlan;
+	size_t flex_size;
 
 	if (tvlv_value_len < sizeof(*tt_data))
 		return;
@@ -3998,17 +3987,18 @@ static void batadv_tt_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
 
 	num_vlan = ntohs(tt_data->num_vlan);
 
-	if (tvlv_value_len < sizeof(*tt_vlan) * num_vlan)
+	flex_size = flex_array_size(tt_data, vlan_data, num_vlan);
+	if (tvlv_value_len < flex_size)
 		return;
 
-	tt_vlan = (struct batadv_tvlv_tt_vlan_data *)(tt_data + 1);
-	tt_change = (struct batadv_tvlv_tt_change *)(tt_vlan + num_vlan);
-	tvlv_value_len -= sizeof(*tt_vlan) * num_vlan;
+	tt_change = (struct batadv_tvlv_tt_change *)(tt_data->vlan_data +
+						     num_vlan);
+	tvlv_value_len -= flex_size;
 
 	num_entries = batadv_tt_entries(tvlv_value_len);
 
-	batadv_tt_update_orig(bat_priv, orig, tt_vlan, num_vlan, tt_change,
-			      num_entries, tt_data->ttvn);
+	batadv_tt_update_orig(bat_priv, orig, tt_data->vlan_data, num_vlan,
+			      tt_change, num_entries, tt_data->ttvn);
 }
 
 /**
@@ -4039,8 +4029,7 @@ static int batadv_tt_tvlv_unicast_handler_v1(struct batadv_priv *bat_priv,
 	tt_data = tvlv_value;
 	tvlv_value_len -= sizeof(*tt_data);
 
-	tt_vlan_len = sizeof(struct batadv_tvlv_tt_vlan_data);
-	tt_vlan_len *= ntohs(tt_data->num_vlan);
+	tt_vlan_len = flex_array_size(tt_data, vlan_data, tt_data->num_vlan);
 
 	if (tvlv_value_len < tt_vlan_len)
 		return NET_RX_SUCCESS;
-- 
2.25.1

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