6.11-stable review patch. If anyone has any objections, please let me know.
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From: Christian Brauner brauner@kernel.org
commit 8a46067783bdff222d1fb8f8c20e3b7b711e3ce5 upstream.
When we access a no-current task's pid namespace we need check that the task hasn't been reaped in the meantime and it's pid namespace isn't accessible anymore.
The user namespace is fine because it is only released when the last reference to struct task_struct is put and exit_creds() is called.
Link: https://lore.kernel.org/r/20240926-klebt-altgedienten-0415ad4d273c@brauner Fixes: 5b08bd408534 ("pidfs: allow retrieval of namespace file descriptors") CC: stable@vger.kernel.org # v6.11 Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/pidfs.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/pidfs.c b/fs/pidfs.c index 7ffdc88dfb52..80675b6bf884 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -120,6 +120,7 @@ static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg) struct nsproxy *nsp __free(put_nsproxy) = NULL; struct pid *pid = pidfd_pid(file); struct ns_common *ns_common = NULL; + struct pid_namespace *pid_ns;
if (arg) return -EINVAL; @@ -202,7 +203,9 @@ static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case PIDFD_GET_PID_NAMESPACE: if (IS_ENABLED(CONFIG_PID_NS)) { rcu_read_lock(); - ns_common = to_ns_common( get_pid_ns(task_active_pid_ns(task))); + pid_ns = task_active_pid_ns(task); + if (pid_ns) + ns_common = to_ns_common(get_pid_ns(pid_ns)); rcu_read_unlock(); } break;