linux-kernel - [PATCH 4/4] signal: allow to send any siginfo to itself

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Date:	Mon, 24 Dec 2012 12:13:27 +0400
From:	Andrey Vagin <avagin@...nvz.org>
To:	linux-kernel@...r.kernel.org
Cc:	criu@...nvz.org, linux-fsdevel@...r.kernel.org,
	Andrey Vagin <avagin@...nvz.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: [PATCH 4/4] signal: allow to send any siginfo to itself

A kernel prevents of sending siginfo with positive si_code, because
these codes is reserved for kernel. I think we can allow to send any
siginfo to itself. This operation should not be dangerous.

This functionality is required for restoring signals.

Cc: Serge Hallyn <serge.hallyn@...onical.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Pavel Emelyanov <xemul@...allels.com>
CC: Cyrill Gorcunov <gorcunov@...nvz.org>
Signed-off-by: Andrey Vagin <avagin@...nvz.org>
---
 kernel/signal.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 91bb76f2..1c83c71 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2957,7 +2957,8 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
 	/* 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) {
+	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);
 		return -EPERM;
@@ -2977,7 +2978,8 @@ long 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) {
+	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);
 		return -EPERM;
-- 
1.7.11.7

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