su starts behaving oddly sometimes on F19

Tomas Mraz tmraz at
Fri May 17 10:33:16 UTC 2013

On Thu, 2013-05-16 at 22:29 -0700, Adam Williamson wrote: 
> This is a weird bug I've seen 3 or 4 times since upgrading to F19, and
> am having trouble pinning down.
> Occasionally, after my session has been up for some time, runs of 'su'
> start behaving oddly. After I enter the root password, it takes a long
> time - longer than the delay that's always happened when you fat-finger
> your password, even - before it succeeds. Usually, of course, it's
> instant. But when this bug happens, I just get to sit there while it
> thinks about it for like 10-15 seconds before I eventually get a root
> prompt.
> This only applies to my desktop session - but it applies to any terminal
> running in the desktop. At least, it applies to gnome-terminal (even if
> closed and opened again) and xterm. But if I go to ctrl-alt-f2, login,
> and run an 'su', that still returns instantly.
> I've tried strace'ing su, but interestingly, I can't get it to work:
> running su via strace always seems to result in "Authentication
> failure" (which doesn't display this bug; it's only _normally_ slow, the
> same slowness that has always been the case when you fail the password).
> So I'm kinda stuck, really. Has anyone else seen this? Any bright ideas
> for debugging it? Thanks!

Try attaching the strace (as root) to the su process when it waits for
the password.

Tomas Mraz
No matter how far down the wrong road you've gone, turn back.
                                              Turkish proverb

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