do_fork() denies CLONE_THREAD | CLONE_PARENT if NEWUSER | NEWPID.
Then later copy_process() denies CLONE_SIGHAND if the new process
will be in a different pid namespace (task_active_pid_ns() doesn't
match current->nsproxy->pid_ns).
This looks confusing and inconsistent. CLONE_NEWPID is very similar
to the case when ->pid_ns was already unshared, we want the same
restrictions so copy_process() should also nack CLONE_PARENT.
And it would be better to deny CLONE_NEWUSER && CLONE_SIGHAND as
well just for consistency.
Kill the "CLONE_NEWUSER | CLONE_NEWPID" check in do_fork() and
change copy_process() to the same check along with nsproxy->pid_ns
we already have.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
kernel/fork.c | 22 ++++++++--------------
1 files changed, 8 insertions(+), 14 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 8d56338..fae2ff7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1173,12 +1173,15 @@ static struct task_struct *copy_process(unsigned long
clone_flags,
return ERR_PTR(-EINVAL);
/*
- * If the new process will be in a different pid namespace don't
- * allow the creation of threads, or share the signal handlers.
+ * If the new process will be in a different pid or user namespace
+ * don't allow the creation of threads, or share the signal handlers,
+ * or share the parent.
*/
- if ((clone_flags & CLONE_SIGHAND) &&
- (task_active_pid_ns(current) != current->nsproxy->pid_ns))
- return ERR_PTR(-EINVAL);
+ if (clone_flags & (CLONE_SIGHAND | CLONE_PARENT)) {
+ if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
+ (task_active_pid_ns(current) != current->nsproxy->pid_ns))
+ return ERR_PTR(-EINVAL);
+ }
retval = security_task_create(clone_flags);
if (retval)
@@ -1575,15 +1578,6 @@ long do_fork(unsigned long clone_flags,
long nr;
/*
- * Do some preliminary argument and permissions checking before we
- * actually start allocating stuff
- */
- if (clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) {
- if (clone_flags & (CLONE_THREAD|CLONE_PARENT))
- return -EINVAL;
- }
-
- /*
* Determine whether and which event to report to ptracer. When
* called from kernel_thread or CLONE_UNTRACED is explicitly
* requested, no event is reported; otherwise, report if the event
--
1.5.5.1
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