Re: udev-140 Bug: udevadm test changing mode of /dev to 660, so making /dev unusuable for users

[Matthias Schwarzott <zzam@gentoo.org>]

On Mittwoch, 18. März 2009, Matthias Schwarzott wrote:
> Hi there!
>
> This time I have a very strange error. I tried what happens when using
> # udevadm test /sys/class/mem/null
>
> and strange, a bit later some user processes had problems accessing
> /dev/null. A quick check showed, that the permissions of /dev were
> destroyed.
>
> # ls -ld /dev /dev/null
> drw-rw---- 16 root root 4280 18. Mär 11:14 /dev
> crw-rw-rw-  1 root root 1, 3 17. Mär 08:05 /dev/null
>

I found out how the error occurs:
It is a difference between
A. udevadm test /sys/class/mem/null/
and
B. udevadm test /sys/class/mem/null

Case A was the case that showed the error behaviour. It seems udevadm is 
confused by the trailing slash. This behaviour seems to be there since ages. 
So there are 2 things that might be done.
1. Make the code more robust, fix error path of failing rename operation to 
not call chmod after it. (I did not fully understand this code).
2. Catch the above case and either strip of the trailing slash or add a better 
solution that normalizes the path and extracts "KERNEL".

Regards
Matthias