receive-pack: fix deadlock when we cannot create tmpdir

The err_fd descriptor passed to the unpack() function is
intended to be handed off to the child index-pack, and our
async muxer will read until it gets EOF. However, if we
encounter an error before handing off the descriptor, we
must manually close(err_fd). Otherwise we will be waiting
for our muxer to finish, while the muxer is waiting for EOF
on err_fd.

We fixed an identical deadlock already in 49ecfa13f
(receive-pack: close sideband fd on early pack errors,
2013-04-19). But since then, the function grew a new
early-return in 722ff7f87 (receive-pack: quarantine objects
until pre-receive accepts, 2016-10-03), when we fail to
create a temporary directory. This return needs the same
treatment.

Reported-by: Horst Schirmeier <horst@schirmeier.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index e6b3879a5b90034937dfb8eee32f8d2981f6bb53..eb6d25a14951426c1a0ad00dafe3b228739391cb 100644 (file)
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1664,8 +1664,11 @@ static const char *unpack(int err_fd, struct shallow_info *si)
        }
 
        tmp_objdir = tmp_objdir_create();
-       if (!tmp_objdir)
+       if (!tmp_objdir) {
+               if (err_fd > 0)
+                       close(err_fd);
                return "unable to create temporary object directory";
+       }
        child.env = tmp_objdir_env(tmp_objdir);
 
        /*