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prefix_ref_iterator: don't trim too much 

The `trim` parameter can be set independently of `prefix`. So if some
caller were to set `trim` to be greater than `strlen(prefix)`, we
could end up pointing the `refname` field of the iterator past the NUL
of the actual reference name string.

That can't happen currently, because `trim` is always set either to
zero or to `strlen(prefix)`. But even the latter could lead to
confusion, if a refname is exactly equal to the prefix, because then
we would set the outgoing `refname` to the empty string.

And we're about to decouple the `prefix` and `trim` arguments even
more, so let's be cautious here. Report a bug if ever asked to trim a
reference whose name is not longer than `trim`.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Michael Haggerty 2017-05-22 16:17:35 +02:00 committed by Junio C Hamano
parent 04aea8d4df
commit b9c8e7f2fb
1 changed files with 17 additions and 1 deletions
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16
refs/iterator.c
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@ -292,7 +292,23 @@ static int prefix_ref_iterator_advance(struct ref_iterator *ref_iterator)
if (!starts_with(iter->iter0->refname, iter->prefix))
continue;

if (iter->trim) {
/*
* It is nonsense to trim off characters that
* you haven't already checked for via a
* prefix check, whether via this
* `prefix_ref_iterator` or upstream in
* `iter0`). So if there wouldn't be at least
* one character left in the refname after
* trimming, report it as a bug:
*/
if (strlen(iter->iter0->refname) <= iter->trim)
die("BUG: attempt to trim too many characters");
iter->base.refname = iter->iter0->refname + iter->trim;
} else {
iter->base.refname = iter->iter0->refname;
}

iter->base.oid = iter->iter0->oid;
iter->base.flags = iter->iter0->flags;
return ITER_OK;