From: Borislav Petkov <bp@suse.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirsky <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Dave Hansen <dave.hansen@intel.com>,
Greg KH <gregkh@linuxfoundation.org>,
keescook@google.com, hughd@google.com,
Brian Gerst <brgerst@gmail.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Rik van Riel <riel@redhat.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>,
David Laight <David.Laight@aculab.com>,
Eduardo Valentin <eduval@amazon.com>,
aliguori@amazon.com, Will Deacon <will.deacon@arm.com>,
daniel.gruss@iaik.tugraz.at,
Dave Hansen <dave.hansen@linux.intel.com>,
Ingo Molnar <mingo@kernel.org>,
moritz.lipp@iaik.tugraz.at, linux-mm@kvack.org,
richard.fellner@student.tugraz.at,
michael.schwarz@iaik.tugraz.at
Subject: Re: [patch 28/60] x86/mm/kpti: Disable global pages if KERNEL_PAGE_TABLE_ISOLATION=y
Date: Tue, 5 Dec 2017 15:34:53 +0100 [thread overview]
Message-ID: <20171205143453.asr5hyk33me73ana@pd.tnic> (raw)
In-Reply-To: <20171204150607.150578521@linutronix.de>
On Mon, Dec 04, 2017 at 03:07:34PM +0100, Thomas Gleixner wrote:
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> Global pages stay in the TLB across context switches. Since all contexts
> share the same kernel mapping, these mappings are marked as global pages
> so kernel entries in the TLB are not flushed out on a context switch.
>
> But, even having these entries in the TLB opens up something that an
> attacker can use, such as the double-page-fault attack:
>
> http://www.ieee-security.org/TC/SP2013/papers/4977a191.pdf
>
> That means that even when KERNEL_PAGE_TABLE_ISOLATION switches page tables
> on return to user space the global pages would stay in the TLB cache.
>
> Disable global pages so that kernel TLB entries can be flushed before
> returning to user space. This way, all accesses to kernel addresses from
> userspace result in a TLB miss independent of the existence of a kernel
> mapping.
>
> Supress global pages via the __supported_pte_mask. The user space
"Suppress"
Otherwise
Reviewed-by: Borislav Petkov <bp@suse.de>
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix ImendA?rffer, Jane Smithard, Graham Norton, HRB 21284 (AG NA 1/4 rnberg)
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next prev parent reply other threads:[~2017-12-05 14:35 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20171204140706.296109558@linutronix.de>
2017-12-04 14:07 ` [patch 24/60] x86/paravirt: Dont patch flush_tlb_single Thomas Gleixner
2017-12-05 12:18 ` Juergen Gross
2017-12-04 14:07 ` [patch 28/60] x86/mm/kpti: Disable global pages if KERNEL_PAGE_TABLE_ISOLATION=y Thomas Gleixner
2017-12-05 14:34 ` Borislav Petkov [this message]
2017-12-04 14:07 ` [patch 29/60] x86/mm/kpti: Prepare the x86/entry assembly code for entry/exit CR3 switching Thomas Gleixner
2017-12-04 14:07 ` [patch 48/60] x86/mm: Move the CR3 construction functions to tlbflush.h Thomas Gleixner
2017-12-04 14:07 ` [patch 49/60] x86/mm: Remove hard-coded ASID limit checks Thomas Gleixner
2017-12-04 14:07 ` [patch 50/60] x86/mm: Put MMU to hardware ASID translation in one place Thomas Gleixner
2017-12-04 14:08 ` [patch 56/60] x86/mm/kpti: Disable native VSYSCALL Thomas Gleixner
2017-12-04 22:33 ` Andy Lutomirski
2017-12-04 14:08 ` [patch 57/60] x86/mm/kpti: Add Kconfig Thomas Gleixner
2017-12-04 16:54 ` Andy Lutomirski
2017-12-04 16:57 ` Thomas Gleixner
2017-12-05 9:34 ` Thomas Gleixner
2017-12-04 14:08 ` [patch 59/60] x86/mm/dump_pagetables: Check user space page table for WX pages Thomas Gleixner
2017-12-04 14:08 ` [patch 60/60] x86/mm/debug_pagetables: Allow dumping current pagetables Thomas Gleixner
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