Patch "kernel/signal.c: unexport sigsuspend()" has been added to the 3.14-stable tree

Patch "kernel/signal.c: unexport sigsuspend()" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    kernel/signal.c: unexport sigsuspend()

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kernel-signal.c-unexport-sigsuspend.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9d8a765211335cfdad464b90fb19f546af5706ae Mon Sep 17 00:00:00 2001
From: Richard Weinberger <richard@nod.at>
Date: Fri, 20 Nov 2015 15:57:21 -0800
Subject: kernel/signal.c: unexport sigsuspend()

From: Richard Weinberger <richard@nod.at>

commit 9d8a765211335cfdad464b90fb19f546af5706ae upstream.

sigsuspend() is nowhere used except in signal.c itself, so we can mark it
static do not pollute the global namespace.

But this patch is more than a boring cleanup patch, it fixes a real issue
on UserModeLinux.  UML has a special console driver to display ttys using
xterm, or other terminal emulators, on the host side.  Vegard reported
that sometimes UML is unable to spawn a xterm and he's facing the
following warning:

  WARNING: CPU: 0 PID: 908 at include/linux/thread_info.h:128 sigsuspend+0xab/0xc0()

It turned out that this warning makes absolutely no sense as the UML
xterm code calls sigsuspend() on the host side, at least it tries.  But
as the kernel itself offers a sigsuspend() symbol the linker choose this
one instead of the glibc wrapper.  Interestingly this code used to work
since ever but always blocked signals on the wrong side.  Some recent
kernel change made the WARN_ON() trigger and uncovered the bug.

It is a wonderful example of how much works by chance on computers. :-)

Fixes: 68f3f16d9ad0f1 ("new helper: sigsuspend()")
Signed-off-by: Richard Weinberger <richard@nod.at>
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 include/linux/signal.h |    1 -
 kernel/signal.c        |    2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -247,7 +247,6 @@ extern int sigprocmask(int, sigset_t *,
 extern void set_current_blocked(sigset_t *);
 extern void __set_current_blocked(const sigset_t *);
 extern int show_unhandled_signals;
-extern int sigsuspend(sigset_t *);
 
 struct sigaction {
 #ifndef __ARCH_HAS_IRIX_SIGACTION
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3550,7 +3550,7 @@ SYSCALL_DEFINE0(pause)
 
 #endif
 
-int sigsuspend(sigset_t *set)
+static int sigsuspend(sigset_t *set)
 {
 	current->saved_sigmask = current->blocked;
 	set_current_blocked(set);


Patches currently in stable-queue which might be from richard@nod.at are

queue-3.14/kernel-signal.c-unexport-sigsuspend.patch