Messages in this thread |  | | | Date | Thu, 5 Aug 2010 14:31:47 +0200 | | From | Rodolfo Giometti <> | | Subject | Re: [PATCHv3 05/16] pps: access pps device by direct pointer |
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On Thu, Aug 05, 2010 at 03:42:31PM +0400, Alexander Gordeev wrote: > ?? Thu, 5 Aug 2010 11:32:36 +0200 > Rodolfo Giometti <giometti@enneenne.com> ??????????: > > > On Thu, Aug 05, 2010 at 01:06:42AM +0400, Alexander Gordeev wrote: > > > Using device index as a pointer needs some unnecessary work to be done > > > every time the pointer is needed (in irq handler for example). > > > Using a direct pointer is much more easy (and safe as well). > > > > > > Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su> > [snip] > > > > If you remove these functions you can't be sure anymore that nobodies > > may call pps_event() over a non existent device... > > [snip] > > > By dropping pps_get_source you may be here by a call from (i.e.) a > > serial port driver whose doesn't know if your PPS source is gone or > > not... > > > > I don't understand how your modifications may resolve this problem. > > Well, this can happen only if PPS client module calls pps_event before > calling pps_register_source() or after pps_unregister_source(). This > means that it's broken! If we try to handle/workaround broken clients it
Suppose we are using pps-ldisc client. How can you assure that nobodies may execute pps_tty_close() while you are into the pps_event() related to the same serial port?
You can't disable serial interrupts in order to avoid pps_tty_dcd_change calls...
> affects performance. So we have to choose what is the priority: > security or performance. My guru told me I shouldn't bother too much > about broken kernel-space code which my code interacts with. If it's > broken it should be fixed. Some assertions enabled by DEBUG define are > enough. For me it makes sense but I don't know what should I check here?
I'm sorry but I disagree with you. Kernel code can't allow userland programs to corrupt it!
We are not discussing about security or performance but about reliability.
Ciao,
Rodolfo
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