Bugzilla – Bug 739
ignored SIGPIPE stops sudo early in main() after sigprocmask
Last modified: 2016-06-18 06:01:35 MDT
Created attachment 470 [details] patch to ignore SIGPIPE until init_signals has been called to setup signal handlers For some reason that I have not been able to figure sudo has an ignored SIGPIPE by the time sigemptyset(&mask); sigprocmask(SIG_SETMASK, &mask, NULL); is reached in main() in src/sudo.c when I use it over ssh. Even moving the sigprocmask to the very first line in the main() functions triggers this behavior for me. When all signals are enabled the process then terminates because no handlers are installed as of yet. Here's the strace of the problem: stat("/etc/sudo.conf", 0x7fffb1a39050) = -1 ENOENT (No such file or directory) rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 --- SIGPIPE {si_signo=SIGPIPE, si_code=SI_USER, si_pid=29801, si_uid=3733} --- +++ killed by SIGPIPE +++ For a quick workaround I added sigaddset(&mask, SIGPIPE) before sigprocmask and another call to sigprocmask with an empty mask after init_signals has been called.
Created attachment 471 [details] corrected patched.
Can you provide steps to reproduce the problem?
I wish I could. This is just happening on a single machine and the steps to reproduce on that one are: % ssh speter@littleheron speter@littleheron ~ $ sudo speter@littleheron ~ $ if [[ $? -eq 141 ]]; then echo "failed with SIGPIPE"; fi; failed with SIGPIPE speter@littleheron ~ $ i.e. nothing happens and bash doesn't complain because it ignores processes that are terminated with SIGPIPE. I have absolutely no idea where this SIGPIPE comes from though.
Looks like someone might have run into this problem years ago as well fwiw: https://www.sudo.ws/pipermail/sudo-users/2007-August/003295.html
Sudo already ignores SIGPIPE in cases where it is likely to occur but it has no control over what nss or PAM modules might do. It is probably safest to just ignore SIGPIPE while sudo is running.
Created attachment 472 [details] Ignore SIGPIPE for the duration of sudo and not just in a few select places. I've attached the patch that I've been testing.
Fixed in sudo 1.8.17 which is now available.