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/kernel/sys.c b/kernel/sys.c
index c4d6b59..ccc9eb7 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -112,14 +112,17 @@
void (*pm_power_off_prepare)(void);
+/*
+ * set the priority of a task
+ * - the caller must hold the RCU read lock
+ */
static int set_one_prio(struct task_struct *p, int niceval, int error)
{
- uid_t euid = current_euid();
+ const struct cred *cred = current_cred(), *pcred = __task_cred(p);
int no_nice;
- if (p->cred->uid != euid &&
- p->cred->euid != euid &&
- !capable(CAP_SYS_NICE)) {
+ if (pcred->uid != cred->euid &&
+ pcred->euid != cred->euid && !capable(CAP_SYS_NICE)) {
error = -EPERM;
goto out;
}