checkpatch: add warning for kmalloc/kzalloc with multiply

Protect against sizeof overflows by preferring kmalloc_array/kcalloc over
kmalloc/kzalloc with a sizeof multiply.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -4378,6 +4378,30 @@ sub process {
 			    "Prefer $3(sizeof(*$1)...) over $3($4...)\n" . $herecurr);
 		}
 
+# check for k[mz]alloc with multiplies that could be kmalloc_array/kcalloc
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*(k[mz]alloc)\s*\(\s*($FuncArg)\s*\*\s*($FuncArg)/) {
+			my $oldfunc = $3;
+			my $a1 = $4;
+			my $a2 = $10;
+			my $newfunc = "kmalloc_array";
+			$newfunc = "kcalloc" if ($oldfunc eq "kzalloc");
+			if ($a1 =~ /^sizeof\s*\S/ || $a2 =~ /^sizeof\s*\S/) {
+				if (WARN("ALLOC_WITH_MULTIPLY",
+					 "Prefer $newfunc over $oldfunc with multiply\n" . $herecurr) &&
+				    $fix) {
+					my $r1 = $a1;
+					my $r2 = $a2;
+					if ($a1 =~ /^sizeof\s*\S/) {
+						$r1 = $a2;
+						$r2 = $a1;
+					}
+					$fixed[$linenr - 1] =~ s/\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*(k[mz]alloc)\s*\(\s*($FuncArg)\s*\*\s*($FuncArg)/$1 . ' = ' . "$newfunc(" . trim($r1) . ', ' . trim($r2)/e;
+
+				}
+			}
+		}
+
 # 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*,/) {