linux-kernel - Re: [PATCH V3 04/49] x86/xen: Add xenpv_restore_regs_and_return_to

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

Message-ID: <b8793bbb-a148-6b31-0c92-a0d71e50380d@oracle.com>
Date:   Sat, 16 Oct 2021 14:08:55 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Lai Jiangshan <laijs@...ux.alibaba.com>,
        Jan Beulich <jbeulich@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Juergen Gross <jgross@...e.com>, Peter Anvin <hpa@...or.com>,
        xen-devel@...ts.xenproject.org, Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Stefano Stabellini <sstabellini@...nel.org>
Subject: Re: [PATCH V3 04/49] x86/xen: Add
 xenpv_restore_regs_and_return_to_usermode()


On 10/13/21 11:13 PM, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@...ux.alibaba.com>
>
> While in the native case, PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is the
> trampoline stack.  But XEN pv doesn't use trampoline stack, so
> PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is also the kernel stack.  Hence source
> and destination stacks are identical in that case, which means reusing
> swapgs_restore_regs_and_return_to_usermode() in XEN pv would cause %rsp
> to move up to the top of the kernel stack and leave the IRET frame below
> %rsp, which is dangerous to be corrupted if #NMI / #MC hit as either of
> these events occurring in the middle of the stack pushing would clobber
> data on the (original) stack.
>
> And swapgs_restore_regs_and_return_to_usermode() pushing the IRET frame
> on to the original address is useless and error-prone when there is any
> future attempt to modify the code.
>
> Fixes: 7f2590a110b8 ("x86/entry/64: Use a per-CPU trampoline stack for IDT entries")
> Cc: Jan Beulich <jbeulich@...e.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Juergen Gross <jgross@...e.com>
> Cc: Peter Anvin <hpa@...or.com>
> Cc: xen-devel@...ts.xenproject.org>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>