From: Martijn van Duren <openbsd+got@list.imperialat.at>
Subject: gotd: received unexpected privsep message
To: gameoftrees@openbsd.org
Date: Sun, 01 Jun 2025 21:44:23 +0200

Hello all,

After upgrading my gotd machine to 7.7 I noticed that I couldn't delete
branches anymore. The weird part is that the problems disappear when
running in extra verbose mode (-vv), either daemonized, or foreground.

This could be triggered with both `got send -d <branch>`, and
`git push origin --delete <branch>`.

The "unexpected privsep message" seems to originate from lib/serve.c
inside serve_write(), where inside the
while (curstate != STATE_PACKFILE_RECEIVED) {
loop a GOTD_IMSG_PACKFILE_STATUS is received. Adding the
GOTD_IMSG_PACKFILE_STATUS case from the
while (curstate != STATE_REFS_UPDATED && err == NULL) {
loop seems to make gotd behave as expected.

Note that I consider this diff only as a starting point in a deeper
analysis, since it doesn't explain why this case doesn't seem to be
hit while running in verbose mode. I am not familiar enough with the
g{o,i}t internals to say which messages are allowed at what point
during the transaction, and the whole thing reeks of something racy.

As seen below, the diff has been tested on top of
6f02d0a77cf43f47eebfc9af8ebcfcd0241e6729, which is 0.110 commit id.
I've tried to bisect to see if I could find the culprit commit, but
unfortunately I couldn't go prior to the new imsg API (commit
fd9f46f196aef97157fc2532b99e727b72ea32b2). There's a couple of commits
on/after this commit do remove the branch, but there seems to be
some crash inside gotd during this time, so I'm not sure if that
allows the gotd to get past the unexpected privsep message point.

Hopefully someone with more knowledge of gotd than me can have a stab
at this.

martijn@

diff /home/martijn/src/got
path + /home/martijn/src/got
commit - 6f02d0a77cf43f47eebfc9af8ebcfcd0241e6729
blob - bf8e3261ba0241ac634ea7756c6793870799a9ed
file + lib/serve.c
--- lib/serve.c
+++ lib/serve.c
@@ -1343,6 +1343,11 @@ serve_write(int infd, int outfd, int gotd_sock, const 
 }
 curstate = STATE_PACKFILE_RECEIVED;
 break;
+ case GOTD_IMSG_PACKFILE_STATUS:
+ if (!report_status)
+ break;
+ err = report_unpack_status(&imsg, outfd, chattygot);
+ break;
 default:
 err = got_error(GOT_ERR_PRIVSEP_MSG);
 break;