arm64: kernel: restrict /dev/mem read() calls to linear region

[platform/kernel/linux-rpi.git] / arch / arm64 / mm / mmap.c

diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index 7b0d557..adc208c 100644 (file)
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -18,6 +18,7 @@
 
 #include <linux/elf.h>
 #include <linux/fs.h>
+#include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/export.h>
@@ -103,12 +104,18 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
  */
 int valid_phys_addr_range(phys_addr_t addr, size_t size)
 {
-       if (addr < PHYS_OFFSET)
-               return 0;
-       if (addr + size > __pa(high_memory - 1) + 1)
-               return 0;
-
-       return 1;
+       /*
+        * Check whether addr is covered by a memory region without the
+        * MEMBLOCK_NOMAP attribute, and whether that region covers the
+        * entire range. In theory, this could lead to false negatives
+        * if the range is covered by distinct but adjacent memory regions
+        * that only differ in other attributes. However, few of such
+        * attributes have been defined, and it is debatable whether it
+        * follows that /dev/mem read() calls should be able traverse
+        * such boundaries.
+        */
+       return memblock_is_region_memory(addr, size) &&
+              memblock_is_map_memory(addr);
 }
 
 /*