linux-kernel - [PATCH 05/22] signal: Clear si_sys_private before copying siginfo to userspace

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Date:   Mon, 15 Jan 2018 18:39:52 -0600
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     Al Viro <viro@...iv.linux.org.uk>, Oleg Nesterov <oleg@...hat.com>,
        linux-arch@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 05/22] signal: Clear si_sys_private before copying siginfo to userspace

In preparation for unconditionally copying the whole of siginfo
to userspace clear si_sys_private.  So this kernel internal
value is guaranteed not to make it to userspace.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 kernel/signal.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/signal.c b/kernel/signal.c
index b9e5d825ee46..18aa55c1bb4f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -643,6 +643,9 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
 		spin_unlock(&tsk->sighand->siglock);
 		posixtimer_rearm(info);
 		spin_lock(&tsk->sighand->siglock);
+
+		/* Don't expose the si_sys_private value to userspace */
+		info->si_sys_private = 0;
 	}
 #endif
 	return signr;
-- 
2.14.1