kasan: rearrange stack frame info in reports

- Move printing stack frame info before printing page info.

 - Add object_is_on_stack() check to print_address_description() and add
   a corresponding WARNING to kasan_print_address_stack_frame(). This
   looks more in line with the rest of the checks in this function and
   also allows to avoid complicating code logic wrt line breaks.

 - Clean up comments related to get_address_stack_frame_info().

Link: https://lkml.kernel.org/r/1ee113a4c111df97d168c820b527cda77a3cac40.1646237226.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/kasan/report.c

@@ -259,6 +259,15 @@ static void print_address_description(void *addr, u8 tag)
 		pr_err("\n");
 	}
 
+	if (object_is_on_stack(addr)) {
+		/*
+		 * Currently, KASAN supports printing frame information only
+		 * for accesses to the task's own stack.
+		 */
+		kasan_print_address_stack_frame(addr);
+		pr_err("\n");
+	}
+
 	if (is_vmalloc_addr(addr)) {
 		struct vm_struct *va = find_vm_area(addr);
 
@@ -278,9 +287,6 @@ static void print_address_description(void *addr, u8 tag)
 		dump_page(page, "kasan: bad access detected");
 		pr_err("\n");
 	}
-
-	kasan_print_address_stack_frame(addr);
-	pr_err("\n");
 }
 
 static bool meta_row_is_guilty(const void *row, const void *addr)

mm/kasan/report_generic.c

@@ -211,6 +211,7 @@ static void print_decoded_frame_descr(const char *frame_descr)
 	}
 }
 
+/* Returns true only if the address is on the current task's stack. */
 static bool __must_check get_address_stack_frame_info(const void *addr,
 						      unsigned long *offset,
 						      const char **frame_descr,
@@ -224,13 +225,6 @@ static bool __must_check get_address_stack_frame_info(const void *addr,
 
 	BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
 
-	/*
-	 * NOTE: We currently only support printing frame information for
-	 * accesses to the task's own stack.
-	 */
-	if (!object_is_on_stack(addr))
-		return false;
-
 	aligned_addr = round_down((unsigned long)addr, sizeof(long));
 	mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
 	shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
@@ -269,14 +263,13 @@ void kasan_print_address_stack_frame(const void *addr)
 	const char *frame_descr;
 	const void *frame_pc;
 
+	if (WARN_ON(!object_is_on_stack(addr)))
+		return;
+
 	if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
 					  &frame_pc))
 		return;
 
-	/*
-	 * get_address_stack_frame_info only returns true if the given addr is
-	 * on the current task's stack.
-	 */
 	pr_err("\n");
 	pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
 	       addr, current->comm, task_pid_nr(current), offset);