Re: [PATCH v2 2/2] check-ignore.c, dir.c: fix segfault with '.' argument from repo root

Adam Spiers <git@adamspiers.org> writes:

The description does not match what I understand is happening from the original report, though. The above is more like this, no?

    When check-ignore is run with the '.' argument from the top level of
    a repository, it fed an empty string to hash_name() in name-hash.c
    and caused a segfault, as the function kept reading forever past the
    end of the string.

A point to note is that it is not cleaer why it is a corner case to ask about a pathspec ".". It is a valid question "Is the whole tree ignored by default?", isn't it?

And this sounds like a really bad excuse. If it were "it does not make *any* sense ... because the top level is *never* ignored", then the patch is a perfectly fine optimization that happens to work around the problem, but the use of "much" and "typically" is a sure sign that the design of the fix is iffy. It also shows that the patch is not a fix, but is sweeping the problem under the rug, if there were a valid use case to set the top level to be ignored.

I wonder what would happen if we removed that "&& path[0]" check from the caller, not add the "assume the top is never ignored" workaround, and do something like this to the location that causes segv, so that it can give an answer when asked to hash an empty string?

Does the callchain that goes down to this function have other places that assume they will never see an empty string, like this function does, which I _think_ is the real issue?

 name-hash.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)