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/fs/fuse/dir.c b/fs/fuse/dir.c
index e97a989..95bc22b 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -869,18 +869,25 @@
*/
int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task)
{
+ const struct cred *cred;
+ int ret;
+
if (fc->flags & FUSE_ALLOW_OTHER)
return 1;
- if (task->cred->euid == fc->user_id &&
- task->cred->suid == fc->user_id &&
- task->cred->uid == fc->user_id &&
- task->cred->egid == fc->group_id &&
- task->cred->sgid == fc->group_id &&
- task->cred->gid == fc->group_id)
- return 1;
+ rcu_read_lock();
+ ret = 0;
+ cred = __task_cred(task);
+ if (cred->euid == fc->user_id &&
+ cred->suid == fc->user_id &&
+ cred->uid == fc->user_id &&
+ cred->egid == fc->group_id &&
+ cred->sgid == fc->group_id &&
+ cred->gid == fc->group_id)
+ ret = 1;
+ rcu_read_unlock();
- return 0;
+ return ret;
}
static int fuse_access(struct inode *inode, int mask)