This is a note to let you know that I've just added the patch titled
pidns: fix vfork() after unshare(CLONE_NEWPID)
to the 3.11-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:
pidns-fix-vfork-after-unshare-clone_newpid.patch
and it can be found in the queue-3.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e79f525e99b04390ca4d2366309545a836c03bf1 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Date: Wed, 11 Sep 2013 14:19:38 -0700
Subject: pidns: fix vfork() after unshare(CLONE_NEWPID)
From: Oleg Nesterov <oleg@xxxxxxxxxx>
commit e79f525e99b04390ca4d2366309545a836c03bf1 upstream.
Commit 8382fcac1b81 ("pidns: Outlaw thread creation after
unshare(CLONE_NEWPID)") nacks CLONE_VM if the forking process unshared
pid_ns, this obviously breaks vfork:
int main(void)
{
assert(unshare(CLONE_NEWUSER | CLONE_NEWPID) == 0);
assert(vfork() >= 0);
_exit(0);
return 0;
}
fails without this patch.
Change this check to use CLONE_SIGHAND instead. This also forbids
CLONE_THREAD automatically, and this is what the comment implies.
We could probably even drop CLONE_SIGHAND and use CLONE_THREAD, but it
would be safer to not do this. The current check denies CLONE_SIGHAND
implicitely and there is no reason to change this.
Eric said "CLONE_SIGHAND is fine. CLONE_THREAD would be even better.
Having shared signal handling between two different pid namespaces is
the case that we are fundamentally guarding against."
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reported-by: Colin Walters <walters@xxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Reviewed-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/fork.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1173,10 +1173,11 @@ static struct task_struct *copy_process(
return ERR_PTR(-EINVAL);
/*
- * If the new process will be in a different pid namespace
- * don't allow the creation of threads.
+ * If the new process will be in a different pid namespace don't
+ * allow it to share a thread group or signal handlers with the
+ * forking task.
*/
- if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) &&
+ if ((clone_flags & (CLONE_SIGHAND | CLONE_NEWPID)) &&
(task_active_pid_ns(current) !=
current->nsproxy->pid_ns_for_children))
return ERR_PTR(-EINVAL);
Patches currently in stable-queue which might be from oleg@xxxxxxxxxx are
queue-3.11/uprobes-fix-utask-depth-accounting-in-handle_trampoline.patch
queue-3.11/tty-disassociate_ctty-sends-the-extra-sigcont.patch
queue-3.11/pidns-fix-vfork-after-unshare-clone_newpid.patch
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