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From: Al Viro <viro@zeniv.linux.org.uk>
To: Josef Bacik <josef@toxicpanda.com>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	kernel-team@fb.com, willy@infradead.org
Subject: Re: [PATCH][v2] proc: use vmalloc for our kernel buffer
Date: Thu, 13 Aug 2020 18:31:55 +0100	[thread overview]
Message-ID: <20200813173155.GZ1236603@ZenIV.linux.org.uk> (raw)
In-Reply-To: <9e4d3860-5829-df6f-aad4-44d07c62535b@toxicpanda.com>

On Thu, Aug 13, 2020 at 01:19:18PM -0400, Josef Bacik wrote:

> > in sunrpc proc_dodebug() turns into
> > 		left -= snprintf(buffer, left, "0x%04x\n",
					 ^^^^
					 left + 1, that is.

> > 				 *(unsigned int *) table->data);
> > and that's not the only example.
> > 
> 
> 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,

snprintf() always produces a NUL-terminated string.  And if you are passing 7 as
len, you want 0xf0ad\n to be copied to user.  For that you need 8 passed to
snprintf, and 8-byte buffer given to it.

  reply	other threads:[~2020-08-13 17:32 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-13 14:53 [PATCH] proc: use vmalloc for our kernel buffer Josef Bacik
2020-08-13 14:59 ` Matthew Wilcox
2020-08-13 15:08   ` Josef Bacik
2020-08-13 15:33 ` [PATCH][v2] " Josef Bacik
2020-08-13 15:37   ` Christoph Hellwig
2020-08-13 15:40     ` Josef Bacik
2020-08-13 15:41       ` Christoph Hellwig
2020-08-13 16:20         ` Al Viro
2020-08-13 17:19           ` Josef Bacik
2020-08-13 17:31             ` Al Viro [this message]
2020-08-13 17:36               ` Josef Bacik
2020-08-13 21:10             ` David Laight
2020-08-13 21:31               ` Josef Bacik
2020-08-13 16:19 ` [PATCH] " David Laight
2020-08-13 16:21   ` Al Viro
2020-08-13 17:08   ` Josef Bacik

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