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Add tcsetpgrp_nobg() which acts like tcsetpgrp() but returns -1

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for a background process.  This is safer than blocking SIGTTOU
which would cause tcsetpgrp() to succeed in the background.
This commit is contained in:
Todd C. Miller
2017-03-07 12:29:21 -07:00
parent 2f074d33ab
commit af1482f487
5 changed files with 91 additions and 13 deletions
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16
src/exec_nopty.c
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@@ -394,18 +394,12 @@ dispatch_signal(struct exec_closure_nopty *ec, int signo, char *signame)
* Restore foreground process group, if different.
* Otherwise, we cannot resume some shells (pdksh).
*
* There appears to be a race with shells that do restore
* the controlling group. Sudo can receive SIGTTOU
* if the shell has already changed the controlling tty.
* It is possible that we are no longer the foreground
* process so use tcsetpgrp_nobg() to avoid sudo
* receiving SIGTTOU.
*/
if (saved_pgrp != ppgrp) {
sigset_t set, oset;
sigemptyset(&set);
sigaddset(&set, SIGTTOU);
sigprocmask(SIG_BLOCK, &set, &oset);
(void)tcsetpgrp(fd, saved_pgrp);
sigprocmask(SIG_SETMASK, &oset, NULL);
}
if (saved_pgrp != ppgrp)
tcsetpgrp_nobg(fd, saved_pgrp);
close(fd);
}
} else {