lkml.org 
[lkml]   [2007]   [Jun]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 7/8] fdmap v2 - implement sys_socket2
On Sat, 9 Jun 2007, Davide Libenzi wrote:

> On Sat, 9 Jun 2007, Al Viro wrote:
>
> > That's simply not true. On the current kernel nothing stops you from e.g.
> > picking a random number and using F_DUPFD. Voila - there's your randomized
> > descriptor. Portable to earlier kernels.
> >
> > Moreover, nonsense^H^H^Hq_fd() can be implemented in userland just fine
> > if we allow F_DUPFD to arbitrary number - just pass it a random one *or*
> > base chosen like davedel is doing (constant + 20bit random chosen at start
> > time).
>
> That does not work. Or better, it works but it forces *huge* fdtables to
> be created. To do that, you need "start" to be over NR_FILE, and this
> creates an fdtable bigger than NR_FILE ((pointer-size + a-few-bits) *
> NR_FILE) propagated down to every app you fork.

Keep in mind also, that quite a few places in the code, walk through the
whole fdtable memory. So it is not only a problem of wasted RAM.


- Davide


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-06-09 19:11    [W:0.147 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site