+ checkpatch-fix-the-usage-of-capture-group.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: checkpatch: fix the usage of capture group ( ... )
has been added to the -mm tree.  Its filename is
     checkpatch-fix-the-usage-of-capture-group.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/checkpatch-fix-the-usage-of-capture-group.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/checkpatch-fix-the-usage-of-capture-group.patch

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------------------------------------------------------
From: Mrinal Pandey <mrinalmni@gmail.com>
Subject: checkpatch: fix the usage of capture group ( ... )

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.

Link: https://lkml.kernel.org/r/20200714032352.f476hanaj2dlmiot@mrinalpandey
Fixes: e518e9a59ec3 ("checkpatch: emit an error when there's a diff in a changelog")
Signed-off-by: Mrinal Pandey <mrinalmni@gmail.com>
Reviewed-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Tested-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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

--- a/scripts/checkpatch.pl~checkpatch-fix-the-usage-of-capture-group
+++ a/scripts/checkpatch.pl
@@ -2639,8 +2639,8 @@ 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",
_

Patches currently in -mm which might be from mrinalmni@gmail.com are

checkpatch-fix-the-usage-of-capture-group.patch