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Subject: Re: FW: i386 Linux kernel DoS (clarification)
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Petr Vandrovec <vandrove@vc.cvut.cz>
Cc: Leif Sawyer <lsawyer@gci.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, 2002-11-13 at 21:13, Petr Vandrovec wrote:
> This fixes it for me. I'll have to look at ia32 manual at home, why I
> must do pushl %eax & popfl, as NT should be already cleared by
> do_debug(). I probably miss something obvious, but I do not think that
> adding these three instructions into lcall7/27 fastpath is acceptable.

I dont think you can avoid it without ceasing to be clever. The problem
is Linus or someone pulled a nifty track so that we do an lcall in and
an iret.

lcall doesnt clear NT
iret when it sees NT is set performs a task switch to the link field in
the current TSS. 


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