From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DD53C43381 for ; Sat, 30 Mar 2019 02:15:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D9658218D9 for ; Sat, 30 Mar 2019 02:15:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="gStoy4XW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730289AbfC3CNC (ORCPT ); Fri, 29 Mar 2019 22:13:02 -0400 Received: from mail-yw1-f73.google.com ([209.85.161.73]:33710 "EHLO mail-yw1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730151AbfC3CNC (ORCPT ); Fri, 29 Mar 2019 22:13:02 -0400 Received: by mail-yw1-f73.google.com with SMTP id p73so2972043ywp.0 for ; Fri, 29 Mar 2019 19:13:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=Ja0kZzqxxKAov08rxSFjoq9uqoPnfwCL9G8rzgiIods=; b=gStoy4XWlylFbDyJEt36O9HD8IwxKaUwaR6v0wTlLMzgYliKK7tjoW34TgZgStnX0q wDhaUPXhCG5/t2Btmuu85cLcE4bL5ORUNYmyt9JcDM40/iiqm/JRmYXjXoRdmMjlQ5FV FVHqLVfv86pbhW9w/zCwIAKCPSKBFBHNp1qxlVruIM7K5UZMR0pSvX6fUE9LwueYYIpg oS+TM9+JUhknxu2Gq4HEuQA0N19fTD0Bo2+sIYnWK6lK9YnTbtsPriKsjV/6ukdC6rLY TRHuRL96tbWfLbaqxzb0+s1/4du8FzX5jSicmSc6hMZ/aTJJzKuIY8siU43Zzc5PLn9l ZI1A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=Ja0kZzqxxKAov08rxSFjoq9uqoPnfwCL9G8rzgiIods=; b=USXpmeSjvlGmUP1AvvK2dWUfmwfd6lC5iKfUoZjTMn3gFISyivIZ0AHrWfrhH8aM9v kXBwx6TT04TXRcJ0vNPG2k+7VnC6vDHe8gaS5/56j8eoAp+mIckb3hWuJrhl1QzFcVsC oCv3Bw4WYfyIuOvbBXl/hacsqjOSaTtc72UD8ZhJTPFCV4xgsJzxsbFA7qeaH3e/vTxS Z9wykRqevThy2PhE+8pycFuK/AEdb6HD0YtDP7omakvtpJxt7YqNUZWHAoTftbBZGnan 5aGqEGKYUd1/EzFzR5h2I17XrLG8fmE6vgv6MDEWc3pcBu4dwqnZvlYBJ+YLQQotqka7 tlMA== X-Gm-Message-State: APjAAAUW45+RN3A7eg8bf8gO9Nv3nwd0GR9d7168eLplUUbdz42KGEKD JMDa7GstvW2XTz9T/XkQkL9WauarKg== X-Google-Smtp-Source: APXvYqz/zOD7o54HigpHdUUB2ikgGcqbskLH3aenI1KxUEIF8uuZUKdcXwpVpv1Rt8OSa3BgelFK+q3YvA== X-Received: by 2002:a81:4e8e:: with SMTP id c136mr2541416ywb.9.1553911981854; Fri, 29 Mar 2019 19:13:01 -0700 (PDT) Date: Sat, 30 Mar 2019 03:12:32 +0100 Message-Id: <20190330021232.191205-1-jannh@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.21.0.392.gf8f6787159e-goog Subject: [PATCH] signal: don't silently convert SI_USER signals to non-current pidfd From: Jann Horn To: Christian Brauner , jannh@google.com Cc: Oleg Nesterov , "Eric W. Biederman" , Arnd Bergmann , Thomas Gleixner , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The current sys_pidfd_send_signal() silently turns signals with explicit SI_USER context that are sent to non-current tasks into signals with kernel-generated siginfo. This is unlike do_rt_sigqueueinfo(), which returns -EPERM in this case. If a user actually wants to send a signal with kernel-provided siginfo, they can do that with pidfd_send_signal(pidfd, sig, NULL, 0); so allowing this case is unnecessary. Instead of silently replacing the siginfo, just bail out with an error; this is consistent with other interfaces and avoids special-casing behavior based on security checks. Fixes: 3eb39f47934f ("signal: add pidfd_send_signal() syscall") Signed-off-by: Jann Horn --- kernel/signal.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index b7953934aa99..f98448cf2def 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -3605,16 +3605,11 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, if (unlikely(sig != kinfo.si_signo)) goto err; + /* Only allow sending arbitrary signals to yourself. */ + ret = -EPERM; if ((task_pid(current) != pid) && - (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL)) { - /* Only allow sending arbitrary signals to yourself. */ - ret = -EPERM; - if (kinfo.si_code != SI_USER) - goto err; - - /* Turn this into a regular kill signal. */ - prepare_kill_siginfo(sig, &kinfo); - } + (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL)) + goto err; } else { prepare_kill_siginfo(sig, &kinfo); } -- 2.21.0.392.gf8f6787159e-goog