From e0e8eb54d8ae0c4cfd1d297f6351b08a7f635c5f Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Thu, 16 Mar 2006 10:31:38 -0700 Subject: [PATCH] unshare: Use rcu_assign_pointer when setting sighand The sighand pointer only needs the rcu_read_lock on the read side. So only depending on task_lock protection when setting this pointer is not enough. We also need a memory barrier to ensure the initialization is seen first. Use rcu_assign_pointer as it does this for us, and clearly documents that we are setting an rcu readable pointer. Signed-off-by: Eric W. Biederman Acked-by: Paul E. McKenney Signed-off-by: Linus Torvalds --- kernel/fork.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index ccdfbb16c86d..46060cb24af0 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1569,7 +1569,7 @@ asmlinkage long sys_unshare(unsigned long unshare_flags) if (new_sigh) { sigh = current->sighand; - current->sighand = new_sigh; + rcu_assign_pointer(current->sighand, new_sigh); new_sigh = sigh; } -- cgit v1.2.2 From 2d61b86775a5676a8fba2ba2f0f869564e35c630 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sat, 18 Mar 2006 20:41:10 +0300 Subject: [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 [ 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 --- kernel/fork.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 46060cb24af0..b373322ca497 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1478,9 +1478,7 @@ static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 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; -- cgit v1.2.2