linux-kernel - Re: [PATCH][v2] proc: use vmalloc for our kernel buffer

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Date:   Thu, 13 Aug 2020 17:31:54 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     David Laight <David.Laight@...LAB.COM>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "kernel-team@...com" <kernel-team@...com>,
        "willy@...radead.org" <willy@...radead.org>
Subject: Re: [PATCH][v2] proc: use vmalloc for our kernel buffer

On 8/13/20 5:10 PM, David Laight wrote:
> From: Josef Bacik
>> Sent: 13 August 2020 18:19
> ...
>> We wouldn't even need the extra +1 part, since we're only copying in how much
>> the user wants anyway, we could just go ahead and convert this to
>>
>> left -= snprintf(buffer, left, "0x%04x\n", *(unsigned int *) table->data);
>>
>> and be fine, right?  Or am I misunderstanding what you're looking for?  Thanks,
> 
> Doesn't that need to be scnprintf()?
> IIRC snprintf() returns the number of bytes that would have been
> written were the buffer infinite size?
> (I suspect this is an 'accidental' return value from the original
> SYSV? userspace implementation that just dumped characters that
> wouldn't fit in the buffer somewhere.)
> 

Yeah, if you look at the patches I just sent you'll notice I used scnprintf() 
everywhere.  Thanks,

Josef