Re: FAILED: patch "[PATCH] x86/ldt: Unmap PTEs for the slot before freeing LDT pages" failed to apply to 4.18-stable tree

Sasha Levin
2018-11-25T02:43:30Z

On Fri, Nov 23, 2018 at 02:53:54PM +0300, Kirill A. Shutemov wrote:
>On Mon, Nov 19, 2018 at 12:24:33PM +0000, gregkh@linuxfoundation.org wrote:
>>
>> The patch below does not apply to the 4.18-stable tree.
>> If someone wants it applied there, or to any other stable or longterm
>> tree, then please email the backport, including the original git commit
>> id to <stable@vger.kernel.org>.
>
>>From 13e702f756c72dc7c7f2d16920f3b31c9a154f8c Mon Sep 17 00:00:00 2001
>From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>Date: Fri, 26 Oct 2018 15:28:55 +0300
>Subject: [PATCH 2/2] x86/ldt: Unmap PTEs for the slot before freeing LDT pages
>
>commit a0e6e0831c516860fc7f9be1db6c081fe902ebcf upstream
>
>modify_ldt(2) leaves the old LDT mapped after switching over to the new
>one. The old LDT gets freed and the pages can be re-used.
>
>Leaving the mapping in place can have security implications. The mapping is
>present in the userspace page tables and Meltdown-like attacks can read
>these freed and possibly reused pages.
>
>It's relatively simple to fix: unmap the old LDT and flush TLB before
>freeing the old LDT memory.
>
>This further allows to avoid flushing the TLB in map_ldt_struct() as the
>slot is unmapped and flushed by unmap_ldt_struct() or has never been mapped
>at all.
>
>[ tglx: Massaged changelog and removed the needless line breaks ]
>
>Fixes: f55f0501cbf6 ("x86/pti: Put the LDT in its own PGD if PTI is on")
>Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>Cc: bp@alien8.de
>Cc: hpa@zytor.com
>Cc: dave.hansen@linux.intel.com
>Cc: luto@kernel.org
>Cc: peterz@infradead.org
>Cc: boris.ostrovsky@oracle.com
>Cc: jgross@suse.com
>Cc: bhe@redhat.com
>Cc: willy@infradead.org
>Cc: linux-mm@kvack.org
>Cc: stable@vger.kernel.org
>Link: https://lkml.kernel.org/r/20181026122856.66224-3-kirill.shutemov@linux.intel.com

Queued for 4.18, thank you.

--
Thanks,
Sasha