rtmessage: fix NULL pointer dereference in rtRouted_ReadTextFile

[svc-rdkeportal01]

Issue Fixed

Coverity Defect: FORWARD_NULL
CWE: CWE-476 (NULL Pointer Dereference)
Severity: High
Function: rtRouted_ReadTextFile
File: src/rtmessage/rtrouted.c

Root Cause

The function rtRouted_ReadTextFile has a NULL pointer dereference bug:

1. Line 224: fread(*content, 1, sz, pf) is called
2. Line 226: If fread fails, *content is set to NULL
3. Line 230: (*content)[sz] = 0 is executed unconditionally

This means when fread fails, we try to dereference a NULL pointer, causing a crash.

Changes Made

Before (Buggy):

if(fread(*content, 1, sz, pf) != sz)
{
  free(*content);
  *content = NULL;  // Set to NULL on failure
  rtLog_Error("failed to read file %s. %s", fname, strerror(errno));
  err = RT_FAIL;
}
(*content)[sz] = 0;  // ❌ Dereference NULL if fread failed!
fclose(pf);

After (Fixed):

if(fread(*content, 1, sz, pf) != sz)
{
  free(*content);
  *content = NULL;
  rtLog_Error("failed to read file %s. %s", fname, strerror(errno));
  err = RT_FAIL;
}
else
{
  (*content)[sz] = 0;  // ✅ Only dereference when fread succeeds
}
fclose(pf);

Why This Fix is Correct

1. Prevents crash - NULL termination only happens when *content is valid
2. Proper control flow - Uses else block to ensure mutual exclusivity
3. Maintains functionality - Null termination still happens for successful reads
4. Simple fix - Just adds an else block, no complex logic

Error Handling Flow

Before (Buggy):

fread fails → set *content = NULL → dereference NULL → CRASH

After (Fixed):

fread fails → set *content = NULL → skip null termination → return RT_FAIL (safe)
fread succeeds → null terminate *content → return RT_OK (safe)

Testing

• Verified fix compiles without errors
• Checked that null termination only happens on success
• Confirmed error path doesn't dereference NULL