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author | Eric W. Biederman <ebiederm@xmission.com> | 2018-07-20 15:59:17 -0500 |
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committer | Eric W. Biederman <ebiederm@xmission.com> | 2018-09-16 16:06:21 +0200 |
commit | a8ebd17160ce364fac6647f223991a8f2f1924b9 (patch) | |
tree | b60f5d1aa56620c7e5414ca71f404beb351c1683 | |
parent | 0ab93e9c99f8208c0a1a7b7170c827936268c996 (diff) | |
download | op-kernel-dev-a8ebd17160ce364fac6647f223991a8f2f1924b9.zip op-kernel-dev-a8ebd17160ce364fac6647f223991a8f2f1924b9.tar.gz |
tty_io: Use group_send_sig_info in __do_SACK to note it is a session being killed
Replace send_sig and force_sig in __do_SAK with group_send_sig_info
the general helper for sending a signal to a process group. This is
wordier but it allows specifying PIDTYPE_SID so that the signal code
knows the signal went to a session.
Both force_sig() and send_sig(..., 1) specify SEND_SIG_PRIV and the
new call of group_send_sig_info does that explicitly. This is enough
to ensure even a pid namespace init is killed.
The global init remains unkillable. The guarantee that __do_SAK tries
to provide is a clean path to login to a machine. As the global init is
unkillable, if it chooses to hold open a tty it can violate this
guarantee. A technique other than killing processes would be needed
to provide this guarantee to userspace.
The only difference between force_sig and send_sig when sending
SIGKILL is that SIGNAL_UNKILLABLE is cleared. This has no affect on
the processing of a signal sent with SEND_SIG_PRIV by any process, making
it unnecessary, and not behavior that needs to be preserved.
force_sig was used originally because it did not take as many locks as
send_sig. Today send_sig, force_sig and group_send_sig_info take the
same locks when delivering a signal.
group_send_sig_info also contains a permission check that force_sig
and send_sig do not. However the presence of SEND_SIG_PRIV makes the
permission check a noop. So the permission check does not result
in any behavioral differences.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
-rw-r--r-- | drivers/tty/tty_io.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 32bc3e3..6553247 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2738,7 +2738,7 @@ void __do_SAK(struct tty_struct *tty) do_each_pid_task(session, PIDTYPE_SID, p) { tty_notice(tty, "SAK: killed process %d (%s): by session\n", task_pid_nr(p), p->comm); - send_sig(SIGKILL, p, 1); + group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_SID); } while_each_pid_task(session, PIDTYPE_SID, p); /* Now kill any processes that happen to have the tty open */ @@ -2746,7 +2746,7 @@ void __do_SAK(struct tty_struct *tty) if (p->signal->tty == tty) { tty_notice(tty, "SAK: killed process %d (%s): by controlling tty\n", task_pid_nr(p), p->comm); - send_sig(SIGKILL, p, 1); + group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_SID); continue; } task_lock(p); @@ -2754,7 +2754,7 @@ void __do_SAK(struct tty_struct *tty) if (i != 0) { tty_notice(tty, "SAK: killed process %d (%s): by fd#%d\n", task_pid_nr(p), p->comm, i - 1); - force_sig(SIGKILL, p); + group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_SID); } task_unlock(p); } while_each_thread(g, p); |