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From:   Matteo Croce <mcroce@redhat.com>
To:     linux-kernel@vger.kernel.org, Andy Whitcroft <apw@canonical.com>,
        Joe Perches <joe@perches.com>
Cc:     Kees Cook <keescook@chromium.org>,
        Aaron Tomlin <atomlin@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH] checkpatch.pl: Warn on duplicate sysctl local variable
Date:   Fri, 31 May 2019 01:51:01 +0200
Message-Id: <20190530235101.3248-1-mcroce@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Commit 6a33853c5773 ("proc/sysctl: add shared variables for range check")
adds some shared const variables to be used instead of a local copy in
each source file.
Warn when a chunk duplicates one of these values in a ctl_table struct:

    $ scripts/checkpatch.pl 0001-test-commit.patch
    WARNING: duplicated sysctl range checking value 'zero', consider using the shared one in include/linux/sysctl.h
    #27: FILE: arch/arm/kernel/isa.c:48:
    +               .extra1         = &zero,

    WARNING: duplicated sysctl range checking value 'int_max', consider using the shared one in include/linux/sysctl.h
    #28: FILE: arch/arm/kernel/isa.c:49:
    +               .extra2         = &int_max,

    total: 0 errors, 2 warnings, 14 lines checked

Signed-off-by: Matteo Croce <mcroce@redhat.com>
---
 scripts/checkpatch.pl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 342c7c781ba5..b986bab32af7 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6639,6 +6639,13 @@ sub process {
 				     "unknown module license " . $extracted_string . "\n" . $herecurr);
 			}
 		}
+
+# check for sysctl duplicate constants
+		if ($line =~ /\.extra[12]\s*=\s*&(zero|one|int_max|max_int)\b/) {
+			my $extracted_string = get_quoted_string($line, $rawline);
+			WARN("DUPLICATED_SYSCTL_CONST",
+				"duplicated sysctl range checking value '$1', consider using the shared one in include/linux/sysctl.h" . $extracted_string . "\n" . $herecurr);
+		}
 	}
 
 	# If we have no input at all, then there is nothing to report on
-- 
2.21.0