[PATCH] Bluetooth: Fix a buffer overflow in mgmt_mesh_add()

[Harshit Mogalapalli]

Smatch Warning:
net/bluetooth/mgmt_util.c:375 mgmt_mesh_add() error: __memcpy()
'mesh_tx->param' too small (48 vs 50)

Analysis:

'mesh_tx->param' is array of size 48. This is the destination.
u8 param[sizeof(struct mgmt_cp_mesh_send) + 29]; // 19 + 29 = 48.

But in the caller 'mesh_send' we reject only when len > 50.
len > (MGMT_MESH_SEND_SIZE + 31) // 19 + 31 = 50.

Fixes: b338d91703fa ("Bluetooth: Implement support for Mesh")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>
---
This is based on static analysis, I am unsure if we should put
an upper bound to len(48) instead.

This limit on length changed between v4 and v5 patches of Commit:
("Bluetooth: Implement support for Mesh") in function mesh_send()

v4: https://lore.kernel.org/all/20220511155412.740249-2-brian.gix@xxxxxxxxx/
v5: https://lore.kernel.org/all/20220720194511.320773-2-brian.gix@xxxxxxxxx/
---
 net/bluetooth/mgmt_util.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/mgmt_util.h b/net/bluetooth/mgmt_util.h
index 6a8b7e84293d..bdf978605d5a 100644
--- a/net/bluetooth/mgmt_util.h
+++ b/net/bluetooth/mgmt_util.h
@@ -27,7 +27,7 @@ struct mgmt_mesh_tx {
 	struct sock *sk;
 	u8 handle;
 	u8 instance;
-	u8 param[sizeof(struct mgmt_cp_mesh_send) + 29];
+	u8 param[sizeof(struct mgmt_cp_mesh_send) + 31];
 };
 
 struct mgmt_pending_cmd {
-- 
2.38.1