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@xxxxxxxx>
---
sha1_file.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/sha1_file.c b/sha1_file.c
index 09ad64ce55..10c3a0083d 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1124,10 +1124,14 @@ static int sha1_loose_object_info(const unsigned char *sha1,
} else if ((status = parse_sha1_header_extended(hdr, oi, flags)) < 0)
status = error("unable to parse %s header", sha1_to_hex(sha1));
- if (status >= 0 && oi->contentp)
+ if (status >= 0 && oi->contentp) {
*oi->contentp = unpack_sha1_rest(&stream, hdr,
*oi->sizep, sha1);
- else
+ if (!*oi->contentp) {
+ git_inflate_end(&stream);
+ status = -1;
+ }
+ } else
git_inflate_end(&stream);
munmap(map, mapsize);
--
2.14.2.1117.g65a3442612
