x86/microcode/intel: Fix initrd loading with CONFIG_RANDOMIZE_MEMORY=y

CONFIG_RANDOMIZE_MEMORY=y randomizes the physical memmap and thus the
address where the initrd is located. Therefore, we need to add the
offset KASLR put us to in order to find the initrd again on the AP path.

In the future, we will get rid of the initrd address caching and query
the address on both the BSP and AP paths but that would need more work.

Thanks to Nicolai Stange for the good bisection and debugging work.

Reported-and-tested-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160726095138.3470-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 14 insertions, 2 deletions

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 6515c802346a..0f97ae93441b 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -793,10 +793,10 @@ void __init load_ucode_intel_bsp(void)
 void load_ucode_intel_ap(void)
 {
         struct ucode_blobs *blobs_p;
+        unsigned long *ptrs, start = 0;
         struct mc_saved_data *mcs;
         struct ucode_cpu_info uci;
         enum ucode_state ret;
-        unsigned long *ptrs;
 
 #ifdef CONFIG_X86_32
         mcs     = (struct mc_saved_data *)__pa_nodebug(&mc_saved_data);
@@ -815,8 +815,20 @@ void load_ucode_intel_ap(void)
         if (!mcs->num_saved)
                 return;
 
+        if (blobs_p->valid) {
+                start = blobs_p->start;
+
+#ifdef CONFIG_RANDOMIZE_MEMORY
+                /*
+                 * Pay attention to CONFIG_RANDOMIZE_MEMORY=y as it shuffles
+                 * physmem mapping too and there we have the initrd.
+                 */
+                start += PAGE_OFFSET - __PAGE_OFFSET_BASE;
+#endif
+        }
+
         collect_cpu_info_early(&uci);
-        ret = load_microcode(mcs, ptrs, blobs_p->start, &uci);
+        ret = load_microcode(mcs, ptrs, start, &uci);
         if (ret != UCODE_OK)
                 return;