[CRIU] [PATCH v3 06/26] files: Allow to receive further fds
Kirill Tkhai
ktkhai at virtuozzo.com
Tue Dec 6 09:19:03 PST 2016
On 06.12.2016 20:16, Pavel Emelyanov wrote:
>
>> int recv_fd_from_peer(struct fdinfo_list_entry *fle)
>> {
>> struct fdinfo_list_entry *tmp;
>> int fd, ret;
>>
>> + if (fle->received)
>> + return fle->fe->fd;
>> +again:
>> ret = recv_fds(fle->fe->fd, &fd, 1, (void *)&tmp, sizeof(struct fdinfo_list_entry *));
>> if (ret)
>> return -1;
>>
>> if (tmp != fle) {
>> - pr_err("Received wrong fle\n");
>> - return -1;
>> + pr_info("Further fle=%p, pid=%d\n", tmp, fle->pid);
>> + if (!task_fle(current, fle)) {
>
> OK, so this routine makes sure the fle received sits in current's list.
> Two questions: 1. should we consider receiving of non-current fle as BUG()?
Yes, it's a BUG. We fail restore if so.
> and 2. can we make the same check by comparing fle->pid with current? All
> fle's are in shmem, so contents is accessible by everyone.
It seems to be worse, because if there is a problem with fle, it may point
to a random memory. So fle->pid dereference will finish with SIGSEGV.
>
>> + pr_err("Unexpected fle %p, pid=%d\n", fle, current->pid.virt);
>> + return -1;
>> + }
>> + if (keep_fd_for_future(tmp, fd))
>> + return -1;
>> + goto again;
>> }
>> close(fle->fe->fd);
>> + fle->received = 1;
>>
>> return fd;
>> }
>
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