winedbg: Protect fetch_float() in CPU backends against buffer overflow.

programs/winedbg/be_arm.c

@@ -1859,6 +1859,7 @@ static BOOL be_arm_fetch_float(const struct dbg_lvalue* lvalue, unsigned size, d
     /* FIXME: this assumes that debuggee and debugger use the same
      * representation for reals
      */
+    if (size > sizeof(tmp)) return FALSE;
     if (!memory_read_value(lvalue, size, tmp)) return FALSE;
 
     if (size == sizeof(float)) *ret = *(float*)tmp;

programs/winedbg/be_arm64.c

@@ -256,6 +256,7 @@ static BOOL be_arm64_fetch_float(const struct dbg_lvalue* lvalue, unsigned size,
     /* FIXME: this assumes that debuggee and debugger use the same
      * representation for reals
      */
+    if (size > sizeof(tmp)) return FALSE;
     if (!memory_read_value(lvalue, size, tmp)) return FALSE;
 
     if (size == sizeof(float)) *ret = *(float*)tmp;

programs/winedbg/be_i386.c

@@ -805,6 +805,7 @@ static BOOL be_i386_fetch_float(const struct dbg_lvalue* lvalue, unsigned size,
     /* FIXME: this assumes that debuggee and debugger use the same 
      * representation for reals
      */
+    if (size > sizeof(tmp)) return FALSE;
     if (!memory_read_value(lvalue, size, tmp)) return FALSE;
 
     if (size == sizeof(float)) *ret = *(float*)tmp;

programs/winedbg/be_x86_64.c

@@ -727,6 +727,7 @@ static BOOL be_x86_64_fetch_float(const struct dbg_lvalue* lvalue, unsigned size
     /* FIXME: this assumes that debuggee and debugger use the same
      * representation for reals
      */
+    if (size > sizeof(tmp)) return FALSE;
     if (!memory_read_value(lvalue, size, tmp)) return FALSE;
 
     if (size == sizeof(float)) *ret = *(float*)tmp;