Re: [patch 7/8] fdmap v2 - implement sys_socket2

From: Al Viro
Date: Sat Jun 09 2007 - 12:55:21 EST

On Sat, Jun 09, 2007 at 09:26:34AM -0700, Ulrich Drepper wrote:
> Hash: SHA1
> Al Viro wrote:
> > So which code is supposed to do that open/write in your example? Library?
> > Unmodified application? Application specifically modified to make *that*
> > open() randomized?
> Why should that matter? All of the above.

I asked for real-world example. Can I have one, please?

> In whatever way you look at it, there currently is a problem which
> cannot be solved except with truly horrible, horrible hack (open N
> descriptors and randomly select one to use; yep, horrible, I said so).

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
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