Re: [PATCH 5/5] io_uring/epoll: disallow adding an epoll file to an epoll context

[Jens Axboe <axboe@kernel.dk>]

On 5/12/26 1:50 PM, Christian Brauner wrote:
> On Sun, 03 May 2026 02:49:16 -0600, Jens Axboe <axboe@kernel.dk> wrote:
>> diff --git a/io_uring/epoll.c b/io_uring/epoll.c
>> index 59cd4f009648..42057aab9124 100644
>> --- a/io_uring/epoll.c
>> +++ b/io_uring/epoll.c
>> @@ -62,6 +62,9 @@ int io_epoll_ctl(struct io_kiocb *req, unsigned int issue_flags)
>>  	CLASS(fd, tf)(ie->fd);
>>  	if (fd_empty(tf))
>>  		return -EBADF;
>> +	/* disallow adding an epoll context to another epoll context */
>> +	if (ie->op == EPOLL_CTL_ADD && is_file_epoll(fd_file(tf)))
>> +		return -EINVAL;
> 
> This is the same pattern in epoll itself.
> Might be worth also adding a tiny helper for this that both codepaths
> can reuse.\

My preference would be to just open-code it, then it's immediately
obviously what it does. Unless you feel strongly about it?


-- 
Jens Axboe