Messages in this thread | | | Date | Wed, 3 Jun 2020 17:21:08 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH v3 35/75] x86/head/64: Build k/head64.c with -fno-stack-protector |
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On Tue, May 19, 2020 at 11:15:26AM +0200, Borislav Petkov wrote: > On Tue, Apr 28, 2020 at 05:16:45PM +0200, Joerg Roedel wrote: > > From: Joerg Roedel <jroedel@suse.de> > > > > The code inserted by the stack protector does not work in the early > > boot environment because it uses the GS segment, at least with memory > > encryption enabled. > > Can you elaborate on why is that a problem? > > The stack cookie is not generated that early yet so it should be > comparing %gs:40 to 0.
Yes, and when GS_BASE is 0 it will dereference NULL pointer, which generates a page-fault before the kernel is able to handle it.
Joerg
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