Repository navigation
BUG: shpool attach fails to close file descriptors #369
Description
AI Policy Ack
Ack
What happened
Run this command: shpool attach fd-test --cmd='ls -l /proc/self/fd'
Get output like this:
total 0
lrwx------. 1 codespace codespace 64 May 9 05:26 0 -> /dev/pts/12
lrwx------. 1 codespace codespace 64 May 9 05:26 1 -> /dev/pts/12
lrwx------. 1 codespace codespace 64 May 9 05:26 11 -> /dev/pts/12
lrwx------. 1 codespace codespace 64 May 9 05:26 13 -> /dev/pts/ptmx
lrwx------. 1 codespace codespace 64 May 9 05:26 18 -> /dev/pts/ptmx
lrwx------. 1 codespace codespace 64 May 9 05:26 2 -> /dev/pts/12
lrwx------. 1 codespace codespace 64 May 9 05:26 23 -> /dev/pts/ptmx
lr-x------. 1 codespace codespace 64 May 9 05:26 3 -> /proc/4171019/fd
When we spawn a subprocess, it should only inherit fds 0-2. ls -l will open a third fd to read the target directory. But we shouldn't be inheriting fds like 11,13,18,23.
I guess the issue is the fd is not being opened with O_CLOEXEC? The problem is likely shpool_pty not using that in open call. But then you want to turn it off with FD_SETFD on FD_CLOXEC on fds 0, 1, and 2 just before the exec, so the exec doesn't close them, I guess.
What I expected to happen
Get output like this:
$ ls -l /proc/self/fd
total 0
lrwx------. 1 codespace codespace 64 May 9 05:30 0 -> /dev/pts/15
lrwx------. 1 codespace codespace 64 May 9 05:30 1 -> /dev/pts/15
lrwx------. 1 codespace codespace 64 May 9 05:30 2 -> /dev/pts/15
lr-x------. 1 codespace codespace 64 May 9 05:30 3 -> /proc/292647/fd
To Reproduce
Steps to reproduce the behavior:
shpool attach fd-test --cmd='ls -l /proc/self/fd'
Version info
shpool 0.10.0
Logs
Probably not necessary
Activity
ethanpailes commentedon May 9, 2026
Nice catch, thanks! Do you want to try to fix this (totally fine if not)? It's probably a bit in the weeds of wading through the shell startup code, but I imagine the fix is going to be a relatively small patch.
skissane-medallia commentedon May 13, 2026
@ethanpailes I'd be happy to give it a go... but I'm still waiting on approval from my employer to contribute.
Unfortunately, it is a multi-stage approval process, and realistically it might take another week.
ethanpailes commentedon May 13, 2026
No worries, I'm not rushing for the next release, I'll wait for you to get approval to contribute.