Messages in this thread |  | | Date | Fri, 13 May 2011 20:13:26 +0900 | | From | KOSAKI Motohiro <> | | Subject | Re: [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access |
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Hi
Sorry for the long delay.
> char *get_task_comm(char *buf, struct task_struct *tsk) > { > - /* buf must be at least sizeof(tsk->comm) in size */ > - task_lock(tsk); > - strncpy(buf, tsk->comm, sizeof(tsk->comm)); > - task_unlock(tsk); > + unsigned long seq; > + > + do { > + seq = read_seqbegin(&tsk->comm_lock); > + > + strncpy(buf, tsk->comm, sizeof(tsk->comm)); > + > + } while (read_seqretry(&tsk->comm_lock, seq)); > + > return buf; > }
Can you please explain why we should use seqlock? That said, we didn't use seqlock for /proc items. because, plenty seqlock write may makes readers busy wait. Then, if we don't have another protection, we give the local DoS attack way to attackers.
task->comm is used for very fundamentally. then, I doubt we can assume write is enough rare. Why can't we use normal spinlock?
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