From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH 5/5] net: sock_aio_write: set CMSG_MSG_COMPAT flag if
 is_compat_task
Date: Fri, 26 Feb 2010 01:17:51 -0800 (PST)
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From: David Miller <davem@davemloft.net>
Date: Fri, 26 Feb 2010 01:16:46 -0800 (PST)

> From: Florian Westphal <fwestphal@astaro.com>
> Date: Fri, 19 Feb 2010 13:41:47 +0100
> 
>> @@ -837,6 +837,10 @@ static ssize_t do_sock_write(struct msghdr *msg, struct kiocb *iocb,
>>  	msg->msg_iov = (struct iovec *)iov;
>>  	msg->msg_iovlen = nr_segs;
>>  	msg->msg_flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;
>> +#ifdef CONFIG_COMPAT
>> +	if (is_compat_task())
>> +		msg->msg_flags |= MSG_CMSG_COMPAT;
>> +#endif
>>  	if (sock->type == SOCK_SEQPACKET)
>>  		msg->msg_flags |= MSG_EOR;
>>  
> 
> What if the kernel itself does a socket write, say from a software
> interrupt or to generate events in response to a user event,
> and the current process happens to be a compat task?

BTW, it's again another example of why is_compat_task() is almost
always the wrong thing to use.