linux-kernel - Re: [PATCH 08/30] x86, kaiser: unmap kernel from userspace page tables (core patch)

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: <63daa6c0-76de-ee67-6a77-fef601a22943@linux.intel.com>
Date:   Wed, 22 Nov 2017 14:54:29 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        richard.fellner@...dent.tugraz.at, moritz.lipp@...k.tugraz.at,
        daniel.gruss@...k.tugraz.at, michael.schwarz@...k.tugraz.at,
        luto@...nel.org, torvalds@...ux-foundation.org,
        keescook@...gle.com, hughd@...gle.com, x86@...nel.org
Subject: Re: [PATCH 08/30] x86, kaiser: unmap kernel from userspace page
 tables (core patch)

On 11/20/2017 09:21 AM, Thomas Gleixner wrote:
>> +page tables are switched to the full "kernel" copy.  When the
>> +system switches back to user mode, the user/shadow copy is used.
>> +
>> +The minimalistic kernel portion of the user page tables try to
>> +map only what is needed to enter/exit the kernel such as the
>> +entry/exit functions themselves and the interrupt descriptor
>> +table (IDT).
> s/try to//

Actually, they do _aspire_ "to map only what is needed".  But, there
*is* some non-necessary cruft (like the first C function in an
interrupt).  So, removing this language actually makes the description
less precise.