mm/vmalloc: Fix calculation of direct map addr range

The calculation of the direct map address range to flush was wrong.
This could cause the RO direct map alias to not get flushed. Today
this shouldn't be a problem because this flush is only needed on x86
right now and the spurious fault handler will fix cached RO->RW
translations. In the future though, it could cause the permissions
to remain RO in the TLB for the direct map alias, and then the page
would return from the page allocator to some other component as RO
and cause a crash.

So fix fix the address range calculation so the flush will include the
direct map range.
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Meelis Roos <mroos@linux.ee>
Cc: Nadav Amit <namit@vmware.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 868b104d ("mm/vmalloc: Add flag for freeing of special permsissions")
Link: https://lkml.kernel.org/r/20190527211058.2729-2-rick.p.edgecombe@intel.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

mm/vmalloc.c

@@ -2123,7 +2123,6 @@ static inline void set_area_direct_map(const struct vm_struct *area,
 /* Handle removing and resetting vm mappings related to the vm_struct. */
 static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages)
 {
-	unsigned long addr = (unsigned long)area->addr;
 	unsigned long start = ULONG_MAX, end = 0;
 	int flush_reset = area->flags & VM_FLUSH_RESET_PERMS;
 	int i;
@@ -2135,8 +2134,8 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages)
 	 * execute permissions, without leaving a RW+X window.
 	 */
 	if (flush_reset && !IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) {
-		set_memory_nx(addr, area->nr_pages);
-		set_memory_rw(addr, area->nr_pages);
+		set_memory_nx((unsigned long)area->addr, area->nr_pages);
+		set_memory_rw((unsigned long)area->addr, area->nr_pages);
 	}
 
 	remove_vm_area(area->addr);
@@ -2160,9 +2159,10 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages)
 	 * the vm_unmap_aliases() flush includes the direct map.
 	 */
 	for (i = 0; i < area->nr_pages; i++) {
-		if (page_address(area->pages[i])) {
+		unsigned long addr = (unsigned long)page_address(area->pages[i]);
+		if (addr) {
 			start = min(addr, start);
-			end = max(addr, end);
+			end = max(addr + PAGE_SIZE, end);
 		}
 	}