[PATCH 5.4 125/129] checkpatch: fix the usage of capture group ( ... )

From: Greg Kroah-Hartman
Date: Tue Sep 08 2020 - 15:05:53 EST

From: Mrinal Pandey <mrinalmni@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Tested-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Reviewed-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200714032352.f476hanaj2dlmiot@mrinalpandey
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2576,8 +2576,8 @@ 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+ \@\@/)) {