linux-kernel - [PATCH 4.19 85/88] checkpatch: fix the usage of capture group ( ... )

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Date:   Tue,  8 Sep 2020 17:26:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mrinal Pandey <mrinalmni@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Joe Perches <joe@...ches.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.19 85/88] checkpatch: fix the usage of capture group ( ... )

From: Mrinal Pandey <mrinalmni@...il.com>

commit 13e45417cedbfc44b1926124b1846f5ee8c6ba4a upstream.

The usage of "capture group (...)" in the immediate condition after `&&`
results in `$1` being uninitialized.  This issues a warning "Use of
uninitialized value $1 in regexp compilation at ./scripts/checkpatch.pl
line 2638".

I noticed this bug while running checkpatch on the set of commits from
v5.7 to v5.8-rc1 of the kernel on the commits with a diff content in
their commit message.

This bug was introduced in the script by commit e518e9a59ec3
("checkpatch: emit an error when there's a diff in a changelog").  It
has been in the script since then.

The author intended to store the match made by capture group in variable
`$1`.  This should have contained the name of the file as `[\w/]+`
matched.  However, this couldn't be accomplished due to usage of capture
group and `$1` in the same regular expression.

Fix this by placing the capture group in the condition before `&&`.
Thus, `$1` can be initialized to the text that capture group matches
thereby setting it to the desired and required value.

Fixes: e518e9a59ec3 ("checkpatch: emit an error when there's a diff in a changelog")
Signed-off-by: Mrinal Pandey <mrinalmni@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Tested-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
Reviewed-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
Cc: Joe Perches <joe@...ches.com>
Link: https://lkml.kernel.org/r/20200714032352.f476hanaj2dlmiot@mrinalpandey
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 scripts/checkpatch.pl |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2541,8 +2541,8 @@ sub process {

 # Check if the commit log has what seems like a diff which can confuse patch
 		if ($in_commit_log && !$commit_log_has_diff &&
-		    (($line =~ m@^\s+diff\b.*a/[\w/]+@ &&
-		      $line =~ m@^\s+diff\b.*a/([\w/]+)\s+b/$1\b@) ||
+		    (($line =~ m@^\s+diff\b.*a/([\w/]+)@ &&
+		      $line =~ m@^\s+diff\b.*a/[\w/]+\s+b/$1\b@) ||
 		     $line =~ m@^\s*(?:\-\-\-\s+a/|\+\+\+\s+b/)@ ||
 		     $line =~ m/^\s*\@\@ \-\d+,\d+ \+\d+,\d+ \@\@/)) {
 			ERROR("DIFF_IN_COMMIT_MSG",