From 29cf2eb342bb3b0787afd35c5f5c9eb6bbb5b079 Mon Sep 17 00:00:00 2001
From: Frank Benkert <frank.benkert@avat.de>
Date: Fri, 23 Dec 2016 11:45:21 -0600
Subject: [PATCH] AMV7: CAN: Make delete_filter functions more robust

---
 arch/arm/src/samv7/sam_mcan.c | 50 ++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 6 deletions(-)

diff --git a/arch/arm/src/samv7/sam_mcan.c b/arch/arm/src/samv7/sam_mcan.c
index f6c53306bb..683463be9e 100644
--- a/arch/arm/src/samv7/sam_mcan.c
+++ b/arch/arm/src/samv7/sam_mcan.c
@@ -1907,16 +1907,35 @@ static int mcan_del_extfilter(FAR struct sam_mcan_s *priv, int ndx)
 
   DEBUGASSERT(priv != NULL && priv->config != NULL);
   config = priv->config;
-  DEBUGASSERT(ndx < config->nextfilters);
+
+  /* Check user Parameters */
+
+  DEBUGASSERT(ndx >= 0 || ndx < config->nextfilters);
+
+  if (ndx < 0 || ndx >= config->nextfilters)
+    {
+      return -EINVAL;
+    }
 
   /* Get exclusive excess to the MCAN hardware */
 
   mcan_dev_lock(priv);
 
-  /* Release the filter */
-
   word = ndx >> 5;
   bit  = ndx & 0x1f;
+
+  /* Check if this filter is really assigned */
+
+  if ((priv->extfilters[word] & (1 << bit)) == 0)
+    {
+      /* No, error out */
+
+      mcan_dev_unlock(priv);
+      return -ENOENT;
+    }
+
+  /* Release the filter */
+
   priv->extfilters[word] &= ~(1 << bit);
 
   DEBUGASSERT(priv->nextalloc > 0);
@@ -2137,16 +2156,35 @@ static int mcan_del_stdfilter(FAR struct sam_mcan_s *priv, int ndx)
 
   DEBUGASSERT(priv != NULL && priv->config != NULL);
   config = priv->config;
-  DEBUGASSERT(ndx < config->nstdfilters);
+
+  /* Check Userspace Parameters */
+
+  DEBUGASSERT(ndx >= 0 || ndx < config->nstdfilters);
+
+  if (ndx < 0 || ndx >= config->nstdfilters)
+    {
+      return -EINVAL;
+    }
 
   /* Get exclusive excess to the MCAN hardware */
 
   mcan_dev_lock(priv);
 
-  /* Release the filter */
-
   word = ndx >> 5;
   bit  = ndx & 0x1f;
+
+  /* Check if this filter is really assigned */
+
+  if ((priv->stdfilters[word] & (1 << bit)) == 0)
+    {
+      /* No, error out */
+
+      mcan_dev_unlock(priv);
+      return -ENOENT;
+    }
+
+  /* Release the filter */
+
   priv->stdfilters[word] &= ~(1 << bit);
 
   DEBUGASSERT(priv->nstdalloc > 0);