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Check for process group change in tty_wait_background().

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The calling process's process group can change between PROC_UNLOCK(p)
and PGRP_LOCK(pg) in tty_wait_background(), e.g. by a setpgid() call
from another process. If that happens, the signal is not sent to the
calling process, even if the prior checks determine that one should be
sent.  Re-check that the process group hasn't changed after acquiring
the pgrp lock, and if it has, redo the checks.

PR:	250701
Submitted by:	Jakub Piecuch <j.piecuch96@gmail.com>
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2020-10-28 22:12:47 +00:00
parent 1ef64e3da5
commit 3cbf9dc81c
1 changed files with 13 additions and 0 deletions
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13
sys/kern/tty.c
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@ -474,6 +474,19 @@ tty_wait_background(struct tty *tp, struct thread *td, int sig)
sig = 0;
}
PGRP_LOCK(pg);
/*
* pg may no longer be our process group.
* Re-check after locking process group.
*/
PROC_LOCK(p);
if (p->p_pgrp != pg) {
PROC_UNLOCK(p);
PGRP_UNLOCK(pg);
continue;
}
PROC_UNLOCK(p);
pgsignal(pg, ksi.ksi_signo, 1, &ksi);
PGRP_UNLOCK(pg);