Files
linux/arch/x86/kernel
Kirill A. Shutemov a17989cb9b x86/ldt: Unmap PTEs for the slot before freeing LDT pages
commit a0e6e0831c 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: f55f0501cb ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>
2018-11-27 16:10:50 +01:00
..
2017-08-16 20:40:09 +02:00
2014-10-17 13:40:52 -07:00
2018-01-02 20:31:02 +01:00
2018-11-10 07:48:36 -08:00
2018-03-21 12:06:41 +01:00