fds jumping between processes

fds jumping between processes

[Lluís Batlle i Rossell]

Hello,
here is quite an open bug report... I could not reproduce this again, but it
involves the fds opened of a killed process being passed to another process, or
something like this.

I'm using vanilla 2.6.33.3 in x86_64.
I was using skype, talking through it using alsa, and trying the
'share desktop' feature, it died. Starting it again, it could not open the alsa
device. Using fuser:

...:/dev/snd]$ fuser *
controlC0:           32341
pcmC0D0p:            32341
timer:               32341

Which that was:
$ ps ax | grep 323
32341 ?        S      0:01 /home/xxx/.nix-profile/bin/xpdf /tmp/xxx.pdf

So, after skype (using alsa) died, the xpdf process took the soundcard fds
skype had. It does not make much sense xpdf to use sound... so I guess something
worth looking happened.

I don't have more details. Killing xpdf made the new skype open the alsa device
properly.

Sorry for not having analised the situation better. Now I cannot reproduce it
anymore. Maybe this will make someone knowing say "ah, let me look if ...". I
just thought if this is a bug in the kernel, it can involve security problems.

Thank you,
Lluís.

Re: fds jumping between processes

[Lluís Batlle i Rossell]

Bah, forget it! firefox problem. Sorry for the noise.

On Fri, May 14, 2010 at 11:09:03AM +0200, Lluís Batlle i Rossell wrote:
> Hello,
> here is quite an open bug report... I could not reproduce this again, but it
> involves the fds opened of a killed process being passed to another process, or
> something like this.
> 
> I'm using vanilla 2.6.33.3 in x86_64.
> I was using skype, talking through it using alsa, and trying the
> 'share desktop' feature, it died. Starting it again, it could not open the alsa
> device. Using fuser:
> 
> ...:/dev/snd]$ fuser *
> controlC0:           32341
> pcmC0D0p:            32341
> timer:               32341
> 
> Which that was:
> $ ps ax | grep 323
> 32341 ?        S      0:01 /home/xxx/.nix-profile/bin/xpdf /tmp/xxx.pdf
> 
> So, after skype (using alsa) died, the xpdf process took the soundcard fds
> skype had. It does not make much sense xpdf to use sound... so I guess something
> worth looking happened.
> 
> I don't have more details. Killing xpdf made the new skype open the alsa device
> properly.
> 
> Sorry for not having analised the situation better. Now I cannot reproduce it
> anymore. Maybe this will make someone knowing say "ah, let me look if ...". I
> just thought if this is a bug in the kernel, it can involve security problems.
> 
> Thank you,
> Lluís.