linux-kernel - Re: [PATCH] x86/xen: Delay get_cpu_cap until stack canary is established

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Wed, 21 Mar 2018 17:14:21 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Jason Andryuk <jandryuk@...il.com>, Juergen Gross <jgross@...e.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/xen: Delay get_cpu_cap until stack canary is
 established

On 03/19/2018 12:58 PM, Jason Andryuk wrote:
> Commit 2cc42bac1c79 ("x86-64/Xen: eliminate W+X mappings") introduced a
> call to get_cpu_cap, which is fstack-protected.  This is works on x86-64
> as commit 4f277295e54c ("x86/xen: init %gs very early to avoid page
> faults with stack protector") ensures the stack protector is configured,
> but it it did not cover x86-32.
>
> Delay calling get_cpu_cap until after xen_setup_gdt has initialized the
> stack canary.  Without this, a 32bit PV machine crashes early
> in boot.
> (XEN) Domain 0 (vcpu#0) crashed on cpu#0:
> (XEN) ----[ Xen-4.6.6-xc  x86_64  debug=n  Tainted:    C ]----
> (XEN) CPU:    0
> (XEN) RIP:    e019:[<00000000c10362f8>]
>
> And the PV kernel IP corresponds to init_scattered_cpuid_features
>    0xc10362f8 <+24>:    mov    %gs:0x14,%eax
>
> Fixes 2cc42bac1c79 ("x86-64/Xen: eliminate W+X mappings")
>
> Signed-off-by: Jason Andryuk <jandryuk@...il.com>
>


Applied to for-linus-4.17

-boris