x86/KASLR: Return earliest overlap when avoiding regions

[cascardo/linux.git] / arch / x86 / boot / compressed / kaslr.c

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 81edf99..e55ebcb 100644 (file)
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -279,15 +279,24 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
 #endif
 }
 
-/* Does this memory vector overlap a known avoided area? */
-static bool mem_avoid_overlap(struct mem_vector *img)
+/*
+ * Does this memory vector overlap a known avoided area? If so, record the
+ * overlap region with the lowest address.
+ */
+static bool mem_avoid_overlap(struct mem_vector *img,
+                             struct mem_vector *overlap)
 {
        int i;
        struct setup_data *ptr;
+       unsigned long earliest = img->start + img->size;
+       bool is_overlapping = false;
 
        for (i = 0; i < MEM_AVOID_MAX; i++) {
-               if (mem_overlaps(img, &mem_avoid[i]))
-                       return true;
+               if (mem_overlaps(img, &mem_avoid[i]) &&
+                   mem_avoid[i].start < earliest) {
+                       *overlap = mem_avoid[i];
+                       is_overlapping = true;
+               }
        }
 
        /* Avoid all entries in the setup_data linked list. */
@@ -298,13 +307,15 @@ static bool mem_avoid_overlap(struct mem_vector *img)
                avoid.start = (unsigned long)ptr;
                avoid.size = sizeof(*ptr) + ptr->len;
 
-               if (mem_overlaps(img, &avoid))
-                       return true;
+               if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) {
+                       *overlap = avoid;
+                       is_overlapping = true;
+               }
 
                ptr = (struct setup_data *)(unsigned long)ptr->next;
        }
 
-       return false;
+       return is_overlapping;
 }
 
 static unsigned long slots[KERNEL_IMAGE_SIZE / CONFIG_PHYSICAL_ALIGN];
@@ -361,7 +372,7 @@ static void process_e820_entry(struct e820entry *entry,
                               unsigned long minimum,
                               unsigned long image_size)
 {
-       struct mem_vector region, img;
+       struct mem_vector region, img, overlap;
 
        /* Skip non-RAM entries. */
        if (entry->type != E820_RAM)
@@ -400,7 +411,7 @@ static void process_e820_entry(struct e820entry *entry,
        for (img.start = region.start, img.size = image_size ;
             mem_contains(&region, &img) ;
             img.start += CONFIG_PHYSICAL_ALIGN) {
-               if (mem_avoid_overlap(&img))
+               if (mem_avoid_overlap(&img, &overlap))
                        continue;
                slots_append(img.start);
        }