4.4-stable review patch. If anyone has any objections, please let me know.
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From: Andi Kleen ak@linux.intel.com
commit 10a70416e1f067f6c4efda6ffd8ea96002ac4223 upstream
The L1TF workaround doesn't make any attempt to mitigate speculate accesses to the first physical page for zeroed PTEs. Normally it only contains some data from the early real mode BIOS.
It's not entirely clear that the first page is reserved in all configurations, so add an extra reservation call to make sure it is really reserved. In most configurations (e.g. with the standard reservations) it's likely a nop.
Signed-off-by: Andi Kleen ak@linux.intel.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Josh Poimboeuf jpoimboe@redhat.com Acked-by: Dave Hansen dave.hansen@intel.com Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/setup.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -851,6 +851,12 @@ void __init setup_arch(char **cmdline_p) memblock_reserve(__pa_symbol(_text), (unsigned long)__bss_stop - (unsigned long)_text);
+ /* + * Make sure page 0 is always reserved because on systems with + * L1TF its contents can be leaked to user processes. + */ + memblock_reserve(0, PAGE_SIZE); + early_reserve_initrd();
/*