[PATCH 2/2] signals: send_sigio: use do_send_sig_info() to avoid check_kill_permission()

[Oleg Nesterov <oleg@redhat.com>]

group_send_sig_info()->check_kill_permission() assumes that current
is the sender and uses current_cred().

This is not true in send_sigio_to_task() case. From the security pov
the sender is not current, but the task which did fcntl(F_SETOWN),
that is why we have sigio_perm() which uses the right creds to check.

Fortunately, send_sigio() always sends either SEND_SIG_PRIV or
SI_FROMKERNEL() signal, so check_kill_permission() does nothing. But
still it would be tidier to avoid this bogus security check and save
a couple of cycles.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 fs/fcntl.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- WAIT/fs/fcntl.c~2_SIGIO	2009-06-17 14:11:26.000000000 +0200
+++ WAIT/fs/fcntl.c	2009-08-01 02:40:41.000000000 +0200
@@ -462,11 +462,11 @@ static void send_sigio_to_task(struct ta
 			else
 				si.si_band = band_table[reason - POLL_IN];
 			si.si_fd    = fd;
-			if (!group_send_sig_info(signum, &si, p))
+			if (!do_send_sig_info(signum, &si, p, true))
 				break;
 		/* fall-through: fall back on the old plain SIGIO signal */
 		case 0:
-			group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
+			do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, true);
 	}
 }