Commit 06f1631a authored Sep 23, 2009 by Oleg Nesterov Committed by Linus Torvalds Sep 24, 2009

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>

parent 4a30debf

fs/fcntl.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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);
		}
		}

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