commit 2d61b86775a5676a8fba2ba2f0f869564e35c630
author Oleg Nesterov <oleg@tv-sign.ru> Sat Mar 18 20:41:10 2006 +0300
committer Linus Torvalds <torvalds@g5.osdl.org> Sat Mar 18 10:49:36 2006 -0800
tree afdb967ec1bb3ddd212acdd8f25675c371f7e6e7
parent 265a92856b17524c87da0258ac0d3cec80ae1d35

[PATCH] disable unshare(CLONE_VM) for now

sys_unshare() does mmput(new_mm).  This is not enough if we have
mm->core_waiters.

This patch is a temporary fix for soon to be released 2.6.16.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
[ Checked with Uli: "I'm not planning to use unshare(CLONE_VM).  It's
  not needed for any functionality planned so far.  What we (as in Red
  Hat) need unshare() for now is the filesystem side." ]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/fork.c

diff --git a/kernel/fork.c b/kernel/fork.c
index 46060cb..b373322 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1478,9 +1478,7 @@
 
 	if ((unshare_flags & CLONE_VM) &&
 	    (mm && atomic_read(&mm->mm_users) > 1)) {
-		*new_mmp = dup_mm(current);
-		if (!*new_mmp)
-			return -ENOMEM;
+		return -EINVAL;
 	}
 
 	return 0;