signals: send_sigio: use do_send_sig_info() to avoid check_kill_permission()

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>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stephane eranian <eranian@googlemail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fcntl.c b/fs/fcntl.c
index ae413086db978093123b2a59947d78e23a02a693..50a9889932625503f5a91b1cc0a77b6debb23e43 100644 (file)
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -461,11 +461,11 @@ static void send_sigio_to_task(struct task_struct *p,
                        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);
        }
 }