checkpatch: add check for reuse of krealloc arg

On Thu, 2013-03-14 at 13:30 +0000, David Woodhouse wrote:
> If krealloc() returns NULL, it *doesn't* free the original. So any code
> of the form 'foo = krealloc(foo, …);' is almost certainly a bug.

So add a check for it to checkpatch.

Signed-off-by: Joe Perches <joe@perches.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -3477,6 +3477,13 @@ sub process {
 			     "unnecessary cast may hide bugs, see http://c-faq.com/malloc/mallocnocast.html\n" . $herecurr);
 		}
 
+# check for krealloc arg reuse
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*krealloc\s*\(\s*\1\s*,/) {
+			WARN("KREALLOC_ARG_REUSE",
+			     "Reusing the krealloc arg is almost always a bug\n" . $herecurr);
+		}
+
 # check for alloc argument mismatch
 		if ($line =~ /\b(kcalloc|kmalloc_array)\s*\(\s*sizeof\b/) {
 			WARN("ALLOC_ARRAY_ARGS",