I think you got the answer to your main question. So let me answer on how I did the same thing. And perhaps some ideas on how to get around your issues.

First, I don't bother dropping the modules. In fact, I just put them in to always load during boot, and then forget about it. (Actually, since moving to Gentoo, I just compiled 'em right into the kernel so they aren't modules anymore.) Then I set /mnt/camera to be mountable by non-root by adding ",user" to the options string. In your case, that would be /mnt/usb/flash.

Next option would be to have a load/unload script, say, /usr/local/bin/mount_flash, which just was: 

#!/bin/sh
unmount=$1
if [ $unmount = "-d" ]
then
  /sbin/umount /mnt/usb/flash
  sleep 2
  /sbin/modprobe -r usb-storage
else
  /sbin/modprobe usb-storage
  /sbin/mount /mnt/usb/flash
fi

[download]
Then add this to /etc/sudoers such that you can run it without a password: 
alaric NOPASSWD: /usr/local/bin/mount_flash, /usr/local/bin/mount_flas
+h -d

[download]
(I think), and now just run system(qw(sudo /usr/local/bin/mount_flash)) and system(qw(sudo /usr/local/bin/mount_flash -d)). Completely avoiding setuid().

In reply to Re: An odd failure of setuid(0) by Tanktalus
in thread An odd failure of setuid(0) by Llew_Llaw_Gyffes

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.