Re: [RFC PATCH 2/7] dir.c: fix off-by-one error in match_pathspec_item

[Elijah Newren]

On Thu, Apr 5, 2018 at 10:49 AM, Jeff King <p...@peff.net> wrote:
>> diff --git a/dir.c b/dir.c
>> index 19212129f0..c915a69385 100644
>> --- a/dir.c
>> +++ b/dir.c
>> @@ -384,7 +384,7 @@ static int match_pathspec_item(const struct 
>> pathspec_item *item, int prefix,
>>       if (flags & DO_MATCH_SUBMODULE) {
>>               /* name is a literal prefix of the pathspec */
>>               if ((namelen < matchlen) &&
>> -                 (match[namelen] == '/') &&
>> +                 (match[namelen-1] == '/') &&
>>                   !ps_strncmp(item, match, name, namelen))
>>                       return MATCHED_RECURSIVELY;
>
> Do we care about matching the name "foo" against the patchspec_item "foo/"?
>
> That matches now, but wouldn't after your patch.

Technically, the tests pass anyway due to the fallback behavior
mentioned in the commit message, but this is a really good point.  It
looks like the call to submodule_path_match() from builtin/grep.c is
going to be passing name without the trailing '/', which is contrary
to how read_directory_recursive() in dir.c builds up paths (namely
with the trailing '/'). If we tried to force consistency (either
always omit the trailing slash or always include it), then we'd
probably want to do so for match_pathspec() calls as well, and there
are lots of those throughout the code and auditing it all looks
painful.

So I should probably make the check handle both cases:

@@ -383,8 +383,9 @@ static int match_pathspec_item(const struct
pathspec_item *item, int prefix,
        /* Perform checks to see if "name" is a super set of the pathspec */
        if (flags & DO_MATCH_LEADING_PATHSPEC) {
                /* name is a literal prefix of the pathspec */
+               int offset = name[namelen-1] == '/' ? 1 : 0;
                if ((namelen < matchlen) &&
-                   (match[namelen] == '/') &&
+                   (match[namelen-offset] == '/') &&
                    !ps_strncmp(item, match, name, namelen))
                        return MATCHED_RECURSIVELY_LEADING_PATHSPEC;