linux-kernel - [PATCH 3.14 25/53] signal: remove warning about using SI_TKILL in rt

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Date:	Mon, 25 Jul 2016 13:55:07 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Vladimir Davydov <vdavydov@...allels.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Richard Weinberger <richard@....at>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.14 25/53] signal: remove warning about using SI_TKILL in rt_[tg]sigqueueinfo

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vladimir Davydov <vdavydov@...allels.com>

commit 69828dce7af2cb6d08ef5a03de687d422fb7ec1f upstream.

Sending SI_TKILL from rt_[tg]sigqueueinfo was deprecated, so now we issue
a warning on the first attempt of doing it.  We use WARN_ON_ONCE, which is
not informative and, what is worse, taints the kernel, making the trinity
syscall fuzzer complain false-positively from time to time.

It does not look like we need this warning at all, because the behaviour
changed quite a long time ago (2.6.39), and if an application relies on
the old API, it gets EPERM anyway and can issue a warning by itself.

So let us zap the warning in kernel.

Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
Acked-by: Oleg Nesterov <oleg@...hat.com>
Cc: Richard Weinberger <richard@....at>
Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/signal.c |   14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3004,11 +3004,9 @@ static int do_rt_sigqueueinfo(pid_t pid,
 	 * Nor can they impersonate a kill()/tgkill(), which adds source info.
 	 */
 	if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
-	    (task_pid_vnr(current) != pid)) {
-		/* We used to allow any < 0 si_code */
-		WARN_ON_ONCE(info->si_code < 0);
+	    (task_pid_vnr(current) != pid))
 		return -EPERM;
-	}
+
 	info->si_signo = sig;

 	/* POSIX.1b doesn't mention process groups.  */
@@ -3053,12 +3051,10 @@ static int do_rt_tgsigqueueinfo(pid_t tg
 	/* Not even root can pretend to send signals from the kernel.
 	 * Nor can they impersonate a kill()/tgkill(), which adds source info.
 	 */
-	if (((info->si_code >= 0 || info->si_code == SI_TKILL)) &&
-	    (task_pid_vnr(current) != pid)) {
-		/* We used to allow any < 0 si_code */
-		WARN_ON_ONCE(info->si_code < 0);
+	if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
+	    (task_pid_vnr(current) != pid))
 		return -EPERM;
-	}
+
 	info->si_signo = sig;

 	return do_send_specific(tgid, pid, sig, info);