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SubjectRe: [PATCH 1/3] tools/hv: Fix for long file names from readdir
On Tue, Dec 18, 2012 at 12:38:03PM +0000, Ben Hutchings wrote:
> On Tue, 2012-12-18 at 03:06 -0500, Tomas Hozza wrote:
> > ----- Original Message -----
> > > > This is just for sanity. The value PATH_MAX was chosen after
> > > > discussion
> > > > with K. Y. Srinivasan and Olaf Hering instead of some "magic"
> > > > number like
> > > > 256 or 512.
> > >
> > > PATH_MAX is a magic name.
> >
> > It is defined in "limits.h". I would welcome some more constructive
> > argumentation and critics.
>
> It still bears no relation to any actual limit in the C library or Linux
> kernel. So it's no more valid than the previous number.
>
> In the current context we're enumerating /sys/class/net and we know that
> all the interface names in there are limited to IFNAMSIZ-1 = 15 (there
> is also potentially "bonding_masters"). The longest path name we need
> to use is definitely much shorter than even 256 bytes.
>
> > > > > Using snprintf() is a good idea, but you need to check the return
> > > > > value and handle the truncation case somehow.
> > > >
> > > > By using PATH_MAX sized buffer there is no need for handling the
> > > > truncation
> > > > case.
> > >
> > > You are claiming two contradictory things: sprintf() may overrun the
> > > buffer, so we need the length check provided by snprintf(), but there
> > > is no need to check for truncation because we know the length is
> > > sufficient.
> >
> > So what do you propose? How should it be solved?
>
> if (snprintf(dev_id, sizeof(dev_id), ...) >= sizeof(dev_id))
> continue;
>
> Possibly logging a warning.

I agree, I'm dropping this patch from my to-apply queue.

greg k-h


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