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get_sha1_with_context: always initialize oc->symlink_path

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The get_sha1_with_context() function zeroes out the
oc->symlink_path strbuf, but doesn't use strbuf_init() to
set up the usual invariants (like pointing to the slopbuf).
We don't actually write to the oc->symlink_path strbuf
unless we call get_tree_entry_follow_symlinks(), and that
function does initialize it. However, readers may still look
at the zero'd strbuf.

In practice this isn't a triggerable bug. The only caller
that looks at it only does so when the mode we found is 0.
This doesn't happen for non-tree-entries (where we return
S_IFINVALID). A broken tree entry could have a mode of 0,
but canon_mode() quietly rewrites that into S_IFGITLINK.
So the "0" mode should only come up when we did indeed find
a symlink.

This is mostly just an accident of how the code happens to
work, though. Let's future-proof ourselves to make sure the
strbuf is properly initialized for all calls (it's only a
few struct member assignments, not a heap allocation).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2017-05-19 08:52:25 -04:00 committed by Junio C Hamano
parent c0a487eafb
commit d72cae12b9
2 changed files with 1 additions and 1 deletions
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1
sha1_name.c
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@ -1511,6 +1511,7 @@ static int get_sha1_with_context_1(const char *name,
memset(oc, 0, sizeof(*oc));
oc->mode = S_IFINVALID;
strbuf_init(&oc->symlink_path, 0);
ret = get_sha1_1(name, namelen, sha1, flags);
if (!ret)
return ret;

1
tree-walk.c
View File

@ -589,7 +589,6 @@ enum follow_symlinks_result get_tree_entry_follow_symlinks(unsigned char *tree_s
int i;
init_tree_desc(&t, NULL, 0UL);
strbuf_init(result_path, 0);
strbuf_addstr(&namebuf, name);
hashcpy(current_tree_sha1, tree_sha1);