checkpatch: add check for sscanf without return use

Naked use sscanf can be troublesome because the pointed to variables may
not have been set.

Add a warning when the sscanf return value is not used.

For now, do not add __must_check to the sscanf prototype because that will
cause a couple of hundred new warnings when compiling a kernel.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 1eb5d2fa8d20..61090e0ff613 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4019,6 +4019,23 @@ sub process {
                         }
                 }
 
+# check for naked sscanf
+                if ($^V && $^V ge 5.10.0 &&
+                    defined $stat &&
+                    $stat =~ /\bsscanf\b/ &&
+                    ($stat !~ /$Ident\s*=\s*sscanf\s*$balanced_parens/ &&
+                     $stat !~ /\bsscanf\s*$balanced_parens\s*(?:$Compare)/ &&
+                     $stat !~ /(?:$Compare)\s*\bsscanf\s*$balanced_parens/)) {
+                        my $lc = $stat =~ tr@\n@@;
+                        $lc = $lc + $linenr;
+                        my $stat_real = raw_line($linenr, 0);
+                        for (my $count = $linenr + 1; $count <= $lc; $count++) {
+                                $stat_real = $stat_real . "\n" . raw_line($count, 0);
+                        }
+                        WARN("NAKED_SSCANF",
+                             "unchecked sscanf return value\n" . "$here\n$stat_real\n");
+                }
+
 # check for new externs in .h files.
                 if ($realfile =~ /\.h$/ &&
                     $line =~ /^\+\s*(extern\s+)$Type\s*$Ident\s*\(/s) {