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/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index dd38db4..0e49975 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -2399,25 +2399,33 @@
static int
pfm_bad_permissions(struct task_struct *task)
{
+ const struct cred *tcred;
uid_t uid = current_uid();
gid_t gid = current_gid();
+ int ret;
+
+ rcu_read_lock();
+ tcred = __task_cred(task);
/* inspired by ptrace_attach() */
DPRINT(("cur: uid=%d gid=%d task: euid=%d suid=%d uid=%d egid=%d sgid=%d\n",
uid,
gid,
- task->euid,
- task->suid,
- task->uid,
- task->egid,
- task->sgid));
+ tcred->euid,
+ tcred->suid,
+ tcred->uid,
+ tcred->egid,
+ tcred->sgid));
- return (uid != task->euid)
- || (uid != task->suid)
- || (uid != task->uid)
- || (gid != task->egid)
- || (gid != task->sgid)
- || (gid != task->gid)) && !capable(CAP_SYS_PTRACE);
+ ret = ((uid != tcred->euid)
+ || (uid != tcred->suid)
+ || (uid != tcred->uid)
+ || (gid != tcred->egid)
+ || (gid != tcred->sgid)
+ || (gid != tcred->gid)) && !capable(CAP_SYS_PTRACE);
+
+ rcu_read_unlock();
+ return ret;
}
static int