@@ -5,6 +5,7 @@
#include <linux/sched.h> /* For struct task_struct. */
#include <linux/err.h> /* for IS_ERR_VALUE */
#include <linux/bug.h> /* For BUG_ON. */
+#include <linux/pid_namespace.h> /* For task_active_pid_ns. */
#include <uapi/linux/ptrace.h>
/*
@@ -129,6 +130,37 @@ static inline void ptrace_event(int event, unsigned long message)
}
/**
+ * ptrace_event_pid - possibly stop for a ptrace event notification
+ * @event: %PTRACE_EVENT_* value to report
+ * @pid: process identifier for %PTRACE_GETEVENTMSG to return
+ *
+ * Check whether @event is enabled and, if so, report @event and @pid
+ * to the ptrace parent. @pid is reported as the pid_t seen from the
+ * the ptrace parent's pid namespace.
+ *
+ * Called without locks.
+ */
+static inline void ptrace_event_pid(int event, struct pid *pid)
+{
+ /*
+ * FIXME: There's a potential race if a ptracer in a different pid
+ * namespace than parent attaches between computing message below and
+ * when we acquire tasklist_lock in ptrace_stop(). If this happens,
+ * the ptracer will get a bogus pid from PTRACE_GETEVENTMSG.
+ */
+ unsigned long message = 0;
+ struct pid_namespace *ns;
+
+ rcu_read_lock();
+ ns = task_active_pid_ns(rcu_dereference(current->parent));
+ if (ns)
+ message = pid_nr_ns(pid, ns);
+ rcu_read_unlock();
+
+ ptrace_event(event, message);
+}
+
+/**
* ptrace_init_task - initialize ptrace state for a new child
* @child: new child task
* @ptrace: true if child should be ptrace'd by parent's tracer
@@ -1619,10 +1619,12 @@ long do_fork(unsigned long clone_flags,
*/
if (!IS_ERR(p)) {
struct completion vfork;
+ struct pid *pid;
trace_sched_process_fork(current, p);
- nr = task_pid_vnr(p);
+ pid = get_task_pid(p, PIDTYPE_PID);
+ nr = pid_vnr(pid);
if (clone_flags & CLONE_PARENT_SETTID)
put_user(nr, parent_tidptr);
@@ -1637,12 +1639,14 @@ long do_fork(unsigned long clone_flags,
/* forking complete and child started to run, tell ptracer */
if (unlikely(trace))
- ptrace_event(trace, nr);
+ ptrace_event_pid(trace, pid);
if (clone_flags & CLONE_VFORK) {
if (!wait_for_vfork_done(p, &vfork))
- ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
+ ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
}
+
+ put_pid(pid);
} else {
nr = PTR_ERR(p);
}
This is a note to let you know that I have just added a patch titled ptrace: fix fork event messages across pid namespaces to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 1f8e507b69202669e51041a71e632fe42d9738ba Mon Sep 17 00:00:00 2001 From: Matthew Dempsky <mdempsky@chromium.org> Date: Fri, 6 Jun 2014 14:36:42 -0700 Subject: ptrace: fix fork event messages across pid namespaces commit 4e52365f279564cef0ddd41db5237f0471381093 upstream. When tracing a process in another pid namespace, it's important for fork event messages to contain the child's pid as seen from the tracer's pid namespace, not the parent's. Otherwise, the tracer won't be able to correlate the fork event with later SIGTRAP signals it receives from the child. We still risk a race condition if a ptracer from a different pid namespace attaches after we compute the pid_t value. However, sending a bogus fork event message in this unlikely scenario is still a vast improvement over the status quo where we always send bogus fork event messages to debuggers in a different pid namespace than the forking process. Signed-off-by: Matthew Dempsky <mdempsky@chromium.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Julien Tinnes <jln@chromium.org> Cc: Roland McGrath <mcgrathr@chromium.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- include/linux/ptrace.h | 32 ++++++++++++++++++++++++++++++++ kernel/fork.c | 10 +++++++--- 2 files changed, 39 insertions(+), 3 deletions(-) -- 1.9.1