linux-kernel - [PATCH 3.10 026/180] signal: remove warning about using SI_TKILL in rt

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Message-Id: <1471793510-13022-27-git-send-email-w@1wt.eu>
Date:   Sun, 21 Aug 2016 17:29:16 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Vladimir Davydov <vdavydov@...allels.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>,
        Vinson Lee <vlee@...edesktop.org>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 026/180] signal: remove warning about using SI_TKILL in rt_[tg]sigqueueinfo

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>
Cc: Vinson Lee <vlee@...edesktop.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 kernel/signal.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 4d1f7fa..7b81c53 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3004,11 +3004,9 @@ static int do_rt_sigqueueinfo(pid_t pid, int sig, siginfo_t *info)
 	 * 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 tgid, pid_t pid, int sig, siginfo_t *info)
 	/* 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);
-- 
2.8.0.rc2.1.gbe9624a