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/futex_compat.c b/kernel/futex_compat.c
index 2c3fd5e..d607a5b 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -135,7 +135,7 @@
{
struct compat_robust_list_head __user *head;
unsigned long ret;
- uid_t euid = current_euid();
+ const struct cred *cred = current_cred(), *pcred;
if (!futex_cmpxchg_enabled)
return -ENOSYS;
@@ -151,8 +151,9 @@
if (!p)
goto err_unlock;
ret = -EPERM;
- if (euid != p->cred->euid &&
- euid != p->cred->uid &&
+ pcred = __task_cred(p);
+ if (cred->euid != pcred->euid &&
+ cred->euid != pcred->uid &&
!capable(CAP_SYS_PTRACE))
goto err_unlock;
head = p->compat_robust_list;
