Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752751AbdGHNMV (ORCPT ); Sat, 8 Jul 2017 09:12:21 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:50462 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752097AbdGHNMU (ORCPT ); Sat, 8 Jul 2017 09:12:20 -0400 Date: Sat, 8 Jul 2017 14:12:18 +0100 From: Al Viro To: Markus Trippelsdorf Cc: linux-kernel@vger.kernel.org Subject: Re: commit 67d7ddded32 (waitid(2): leave copyout of siginfo to syscall itself) breaks glibc posix/tst-waitid Message-ID: <20170708131218.GP10672@ZenIV.linux.org.uk> References: <20170708095644.GA272@x4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170708095644.GA272@x4> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2469 Lines: 74 On Sat, Jul 08, 2017 at 11:56:44AM +0200, Markus Trippelsdorf wrote: > Since: > commit 67d7ddded322db99f451a7959d56ed6c70a6c4aa > Author: Al Viro > Date: Sun May 14 20:53:13 2017 -0400 > > waitid(2): leave copyout of siginfo to syscall itself > > the glibc posix/tst-waitid.c testcase fails: > > markus@x4 glibc-build % ./posix/tst-waitid > waitid WNOHANG on stopped status 0 I think I see what's going on... We lose the distinction between "got a PID" and "nothing, but that's not an error" a bit too early waitid() case. Could you see if there are any problems left with the following applied? diff --git a/kernel/exit.c b/kernel/exit.c index 462fc25eec6e..aa5d5e4de804 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1604,9 +1604,6 @@ static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop, wo.wo_rusage = ru; ret = do_wait(&wo); - if (ret > 0) - ret = 0; - put_pid(pid); return ret; } @@ -1617,6 +1614,11 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, struct rusage r; struct waitid_info info = {.status = 0}; long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL); + int signo = 0; + if (err > 0) { + signo = SIGCHLD; + err = 0; + } if (!err) { if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) @@ -1626,7 +1628,7 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, return err; user_access_begin(); - unsafe_put_user(err ? 0 : SIGCHLD, &infop->si_signo, Efault); + unsafe_put_user(signo, &infop->si_signo, Efault); unsafe_put_user(0, &infop->si_errno, Efault); unsafe_put_user((short)info.cause, &infop->si_code, Efault); unsafe_put_user(info.pid, &infop->si_pid, Efault); @@ -1728,6 +1730,11 @@ COMPAT_SYSCALL_DEFINE5(waitid, struct rusage ru; struct waitid_info info = {.status = 0}; long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL); + int signo = 0; + if (err > 0) { + signo = SIGCHLD; + err = 0; + } if (!err && uru) { /* kernel_waitid() overwrites everything in ru */ @@ -1743,7 +1750,7 @@ COMPAT_SYSCALL_DEFINE5(waitid, return err; user_access_begin(); - unsafe_put_user(err ? 0 : SIGCHLD, &infop->si_signo, Efault); + unsafe_put_user(signo, &infop->si_signo, Efault); unsafe_put_user(0, &infop->si_errno, Efault); unsafe_put_user((short)info.cause, &infop->si_code, Efault); unsafe_put_user(info.pid, &infop->si_pid, Efault);