CRED: Use RCU to access another task's creds and to release a task's own creds
Use RCU to access another task's creds and to release a task's own creds.
This means that it will be possible for the credentials of a task to be
replaced without another task (a) requiring a full lock to read them, and (b)
seeing deallocated memory.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index 354c1ff..c5afc98 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -106,6 +106,7 @@
struct proc_event *ev;
__u8 buffer[CN_PROC_MSG_SIZE];
struct timespec ts;
+ const struct cred *cred;
if (atomic_read(&proc_event_num_listeners) < 1)
return;
@@ -115,14 +116,19 @@
ev->what = which_id;
ev->event_data.id.process_pid = task->pid;
ev->event_data.id.process_tgid = task->tgid;
+ rcu_read_lock();
+ cred = __task_cred(task);
if (which_id == PROC_EVENT_UID) {
- ev->event_data.id.r.ruid = task->cred->uid;
- ev->event_data.id.e.euid = task->cred->euid;
+ ev->event_data.id.r.ruid = cred->uid;
+ ev->event_data.id.e.euid = cred->euid;
} else if (which_id == PROC_EVENT_GID) {
- ev->event_data.id.r.rgid = task->cred->gid;
- ev->event_data.id.e.egid = task->cred->egid;
- } else
+ ev->event_data.id.r.rgid = cred->gid;
+ ev->event_data.id.e.egid = cred->egid;
+ } else {
+ rcu_read_unlock();
return;
+ }
+ rcu_read_unlock();
get_seq(&msg->seq, &ev->cpu);
ktime_get_ts(&ts); /* get high res monotonic timestamp */
put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);