[linux-dvb] Re: [DVB] PATCH: Handling failure of dvb_frontend_start in dvb_frontend_open [2.5.69-70]

[Daniele Bellucci <bellucda@tiscali.it>]

----------  Forwarded Message  ----------

Subject: Re: [linux-dvb] [DVB] PATCH: Handling failure of dvb_frontend_start in dvb_frontend_open [2.5.69-70]
Date: Fri, 6 Jun 2003 15:28:24 +0200
From: Daniele Bellucci <bellucda@tiscali.it>
To: Johannes Stezenbach <js@convergence.de>

On Fri 6 June 2003 15:03, Johannes Stezenbach wrote:
> Hi,
>
> Daniele Bellucci wrote:
> > This patch applies both to 2.5.69 and to 2.5.70
>
> ...
>
> > + * Changes:
> > + * 03/06/2003:   handling failure of dvb_frontend_start in
> > dvb_frontend_open + *               Daniele Bellucci
> > <bellucda@tiscali.it>.
>
> [snip]
>
> I made similar changes to dvb-frontend.c some weeks ago. It's
> unfortunate that it takes so much time until they get merged into
> Linus' kernel tree.
>
> Anyway, I would like to know why dvb_frontend_start() would fail
> for you.
>
>
>
> The only reason it failed for me was when running the program
> that open()s the frontend in the debugger, which leads to
> kernel_thread() failure for 2.4.21-rc? since the time the ptrace() exploit
> fixes have been merged.
>
>
> Regards,
> Johannes

Hi Johannes,
there are many reason for kernel_thread to fail ... like:
the allocation of a new struct task_struct (its descriptor) may fail (look at
 dup_task_struct in kernel/fork.c) security_task_create (kernel/fork.c:
 copy_process) can forbid the creation of a new task (in 2.5.x) if the actual
 number of threads is > of max_threads (kernel/fork.c: copy_process) and so
 on...

kernel_thread call do_fork,  then do_fork call copy_process.. there are many
 cases for copy_process to fail.

You should look at copy_process.



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