FAILED: patch "[PATCH] batman-adv: tvlv: reject oversized TVLV packets" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x f50487e3566358b2b982b7801945e858c78ad9ab
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026052839-sample-democracy-7987@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f50487e3566358b2b982b7801945e858c78ad9ab Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <[email protected]>
Date: Sat, 9 May 2026 21:55:29 +0200
Subject: [PATCH] batman-adv: tvlv: reject oversized TVLV packets

batadv_tvlv_container_ogm_append() builds a TVLV packet section from the tvlv.container_list. The total size of this section is computed by batadv_tvlv_container_list_size(), which sums the sizes of all registered containers.

The return type and accumulator in batadv_tvlv_container_list_size() were u16. If the accumulated size exceeds U16_MAX, the value wraps around, causing the subsequent allocation in batadv_tvlv_container_ogm_append() to be undersized. The memcpy-style copy that follows would then write beyond the end of the allocated buffer, corrupting kernel memory.

Fix this by widening the return type of batadv_tvlv_container_list_size() to size_t. In batadv_tvlv_container_ogm_append(), check the computed length against U16_MAX before proceeding, and bail out as if the allocation had failed when the limit is exceeded.

index 46ed61dbf087..cc6ac580c620 100644
@@ -13,6 +13,7 @@
 #include <linux/gfp.h>
 #include <linux/if_ether.h>
 #include <linux/kref.h>
+#include <linux/limits.h>
 #include <linux/list.h>
 #include <linux/lockdep.h>
 #include <linux/netdevice.h>

@@ -160,10 +161,10 @@ batadv_tvlv_container_get(struct batadv_priv *bat_priv, u8 type, u8 version)
  *
  * Return: size of all currently registered tvlv containers in bytes.
  */
-static u16 batadv_tvlv_container_list_size(struct batadv_priv *bat_priv)
+static size_t batadv_tvlv_container_list_size(struct batadv_priv *bat_priv)
 {
 	struct batadv_tvlv_container *tvlv;
-	u16 tvlv_len = 0;
+	size_t tvlv_len = 0;
 
 	lockdep_assert_held(&bat_priv->tvlv.container_list_lock);
 

@@ -316,13 +317,17 @@ int batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
 {
 	struct batadv_tvlv_container *tvlv;
 	struct batadv_tvlv_hdr *tvlv_hdr;
-	u16 tvlv_value_len;
+	size_t tvlv_value_len;
 	void *tvlv_value;
 	int tvlv_len_ret;
 	bool ret;
 
 	spin_lock_bh(&bat_priv->tvlv.container_list_lock);
 	tvlv_value_len = batadv_tvlv_container_list_size(bat_priv);
+	if (tvlv_value_len > U16_MAX) {
+		tvlv_len_ret = -E2BIG;
+		goto end;
+	}
 
 	ret = batadv_tvlv_realloc_packet_buff(packet_buff, packet_buff_len,
 					      packet_min_len, tvlv_value_len);

commit f50487e3566358b2b982b7801945e858c78ad9ab upstream.

batadv_tvlv_container_ogm_append() builds a TVLV packet section from the tvlv.container_list. The total size of this section is computed by batadv_tvlv_container_list_size(), which sums the sizes of all registered containers.

The return type and accumulator in batadv_tvlv_container_list_size() were u16. If the accumulated size exceeds U16_MAX, the value wraps around, causing the subsequent allocation in batadv_tvlv_container_ogm_append() to be undersized. The memcpy-style copy that follows would then write beyond the end of the allocated buffer, corrupting kernel memory.

Fix this by widening the return type of batadv_tvlv_container_list_size() to size_t. In batadv_tvlv_container_ogm_append(), check the computed length against U16_MAX before proceeding, and bail out as if the allocation had failed when the limit is exceeded.

---
 net/batman-adv/tvlv.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

index 75f7ea827ed9d..8da8184a2ebdf 100644
@@ -13,6 +13,7 @@
 #include <linux/if_ether.h>
 #include <linux/kernel.h>
 #include <linux/kref.h>
+#include <linux/limits.h>
 #include <linux/list.h>
 #include <linux/lockdep.h>
 #include <linux/netdevice.h>

@@ -160,10 +161,10 @@ batadv_tvlv_container_get(struct batadv_priv *bat_priv, u8 type, u8 version)
  *
  * Return: size of all currently registered tvlv containers in bytes.
  */
-static u16 batadv_tvlv_container_list_size(struct batadv_priv *bat_priv)
+static size_t batadv_tvlv_container_list_size(struct batadv_priv *bat_priv)
 {
 	struct batadv_tvlv_container *tvlv;
-	u16 tvlv_len = 0;
+	size_t tvlv_len = 0;
 
 	lockdep_assert_held(&bat_priv->tvlv.container_list_lock);
 

@@ -316,13 +317,17 @@ int batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
 {
 	struct batadv_tvlv_container *tvlv;
 	struct batadv_tvlv_hdr *tvlv_hdr;
-	u16 tvlv_value_len;
+	size_t tvlv_value_len;
 	void *tvlv_value;
 	int tvlv_len_ret;
 	bool ret;
 
 	spin_lock_bh(&bat_priv->tvlv.container_list_lock);
 	tvlv_value_len = batadv_tvlv_container_list_size(bat_priv);
+	if (tvlv_value_len > U16_MAX) {
+		tvlv_len_ret = -E2BIG;
+		goto end;
+	}
 
 	ret = batadv_tvlv_realloc_packet_buff(packet_buff, packet_buff_len,
 					      packet_min_len, tvlv_value_len);

2.47.3