[PATCH 4/3] list-objects-filter: use empty string instead of NULL for sparse "base"
- From
Jeff King <peff@peff.net>
- Date
- Sep 15, 2019, 16:51 UTC
- Message-ID
- <20190915165156.GA28436@sigill.intra.peff.net>
- In-Reply-To
- <20190915010942.GA19787@sigill.intra.peff.net>
On Sat, Sep 14, 2019 at 09:09:42PM -0400, Jeff King wrote:
Show 14 quoted lines
> On Mon, Sep 09, 2019 at 01:08:24PM -0400, Jeff King wrote: > > > I'll work up what I sent earlier into a real patch, and include some of > > this discussion. > > Here it is. I pulled Jon's tests out into their own patch (mostly > because it makes it easier to give credit). Then patch 2 is my fix, and > patch 3 is the message fixups he had done. > > This replaces what's queued in js/partial-clone-sparse-blob. > > [1/3]: t5616: test cloning/fetching with sparse:oid=<oid> filter > [2/3]: list-objects-filter: delay parsing of sparse oid > [3/3]: list-objects-filter: give a more specific error sparse parsing error
And here's a bonus patch that I found while running under ASan/UBSan (since I wanted to double-check the memory handling of patch 2 when merged with 'next').
-- >8 -- Subject: list-objects-filter: use empty string instead of NULL for sparse "base"
We use add_excludes_from_blob_to_list() to parse a sparse blob. Since we don't have a base path, we pass NULL and 0 for the base and baselen, respectively. But the rest of the exclude code passes a literal empty string instead of NULL for this case. And indeed, we eventually end up with match_pathname() calling fspathncmp(), which then calls the system strncmp(path, base, baselen).
This works on many platforms, which notice that baselen is 0 and do not look at the bytes of "base" at all. But it does violate the C standard, and building with SANITIZE=undefined will complain. You can also see it by instrumenting fspathncmp like this:
diff --git a/dir.c b/dir.c index d021c908e5..4bb3d3ec96 100644 --- a/dir.c +++ b/dir.c @@ -71,6 +71,8 @@ int fspathcmp(const char *a, const char *b)
int fspathncmp(const char *a, const char *b, size_t count)
{
+ if (!a || !b)
+ BUG("null fspathncmp arguments");
return ignore_case ? strncasecmp(a, b, count) : strncmp(a, b, count);
}We could perhaps be more defensive in match_pathname(), but even if we did so, it makes sense for this code to match the rest of the exclude callers.
Signed-off-by: Jeff King <peff@peff.net> --- list-objects-filter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/list-objects-filter.c b/list-objects-filter.c index 50f0c6d07b..83c788e8b5 100644 --- a/list-objects-filter.c +++ b/list-objects-filter.c @@ -472,7 +472,7 @@ static void *filter_sparse_oid__init( die(_("unable to access sparse blob in '%s'"), filter_options->sparse_oid_name); d->omits = omitted; - if (add_excludes_from_blob_to_list(&sparse_oid, NULL, 0, &d->el) < 0) + if (add_excludes_from_blob_to_list(&sparse_oid, "", 0, &d->el) < 0) die(_("unable to parse sparse filter data in %s"), oid_to_hex(&sparse_oid));
-- 2.23.0.667.gcccf1fbb03