When a caller of sha1_object_info_extended() sets the
"contentp" field in object_info, we call unpack_sha1_rest()
but do not check whether it signaled an error.
This causes two problems:
1. We pass back NULL to the caller via the contentp field,
but the function returns "0" for success. A caller
might reasonably expect after a successful return that
it can access contentp without a NULL check and
segfault.
As it happens, this is impossible to trigger in the
current code. There is exactly one caller which uses
contentp, read_object(). And the only thing it does
after a successful call is to return the content
pointer to its caller, using NULL as a sentinel for
errors. So in effect it converts the success code from
sha1_object_info_extended() back into an error!
But this is still worth addressing avoid problems for
future users of "contentp".
2. Callers of unpack_sha1_rest() are expected to close the
zlib stream themselves on error. Which means that we're
leaking the stream.
The problem in (1) comes from from
c84a1f3ed4 (sha1_file:
refactor read_object, 2017-06-21), which added the contentp
field. Before that, we called unpack_sha1_rest() via
unpack_sha1_file(), which directly used the NULL to signal
an error.
But note that the leak in (2) is actually older than that.
The original unpack_sha1_file() directly returned the result
of unpack_sha1_rest() to its caller, when it should have
been closing the zlib stream itself on error.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>