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From: Alexey Dobriyan <adobriyan@gmail.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 06/13] proc: convert /proc/self to _print_integer()
Date: Thu, 30 Aug 2018 16:13:33 +0300
Message-ID: <20180830131333.GA31422@avx2> (raw)
In-Reply-To: <54cb86c6d96b47bc8017a69be124c105@AcuMS.aculab.com>

On Wed, Aug 29, 2018 at 09:50:50AM +0000, David Laight wrote:
> From: Alexey Dobriyan
> > Sent: 28 August 2018 00:15
> > ---
> >  fs/proc/self.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/proc/self.c b/fs/proc/self.c
> > index 127265e5c55f..b2279412237b 100644
> > --- a/fs/proc/self.c
> > +++ b/fs/proc/self.c
> > @@ -14,6 +14,7 @@ static const char *proc_self_get_link(struct dentry *dentry,
> >  {
> >  	struct pid_namespace *ns = proc_pid_ns(inode);
> >  	pid_t tgid = task_tgid_nr_ns(current, ns);
> > +	char buf[10], *p = buf + sizeof(buf);
> >  	char *name;
> > 
> >  	if (!tgid)
> > @@ -22,7 +23,11 @@ static const char *proc_self_get_link(struct dentry *dentry,
> >  	name = kmalloc(10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);
> >  	if (unlikely(!name))
> >  		return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
> > -	sprintf(name, "%u", tgid);
> > +
> 
> Best not to 'hide' the initialisation of 'p' at the top of the function.
> Much easier to see what is going on if it is moved here.

It was written that way to have initialization near the buffer,
so that it is obvious that pointer and buffer are connected and
making

	p = _print_integer_uNN(p, x);

standard building block which can be copypasted left and right and
still be correct.

> > +	p = _print_integer_u32(p, tgid);
> 
> or just:
> 	p = _print_integer(buf + sizeof(buf), tgid);
> 
> (What a horrid interface ...)

It is. The problem is that adding bound checking will get you current
vsnprintf() and number() and num_to_str().

> > +	memcpy(name, p, buf + sizeof(buf) - p);
> > +	name[buf + sizeof(buf) - p] = '\0';
> > +
> >  	set_delayed_call(done, kfree_link, name);
> >  	return name;
> >  }

  reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-27 23:14 [PATCH 01/13] seq_file: rewrite seq_puts() in terms of seq_write() Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 02/13] proc: apply seq_puts() whenever possible Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 03/13] proc: rename "p" variable in proc_readfd_common() Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 04/13] proc: rename "p" variable in proc_map_files_readdir() Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 05/13] proc: new and improved way to print decimals Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 06/13] proc: convert /proc/self to _print_integer() Alexey Dobriyan
2018-08-29  9:50   ` David Laight
2018-08-30 13:13     ` Alexey Dobriyan [this message]
2018-08-27 23:14 ` [PATCH 07/13] proc: convert /proc/thread-self " Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 08/13] proc: convert /proc/*/fd " Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 09/13] proc: convert dentry flushing on exit " Alexey Dobriyan
2018-08-27 23:15 ` [PATCH 10/13] proc: convert readdir /proc " Alexey Dobriyan
2018-08-27 23:15 ` [PATCH 11/13] proc: readdir /proc/*/task Alexey Dobriyan
2018-08-28 12:36   ` Ahmed S. Darwish
2018-08-28 13:04     ` Ahmed S. Darwish
2018-08-28 19:35       ` Alexey Dobriyan
2018-08-29 23:43         ` Andrew Morton
2018-08-30 13:20           ` Alexey Dobriyan
2018-08-28 19:31     ` Alexey Dobriyan
2018-08-27 23:15 ` [PATCH 12/13] proc: convert /proc/*/statm to _print_integer() Alexey Dobriyan
2018-08-27 23:15 ` [PATCH 13/13] proc: convert /proc/*/task/*/children " Alexey Dobriyan
2018-08-28 18:24 ` [PATCH 01/13] seq_file: rewrite seq_puts() in terms of seq_write() Joe Perches
2018-08-28 20:48   ` Joe Perches
2018-09-03 14:17 ` Alexey Dobriyan

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