rcu: kasan: record and print call_rcu() call stack

Patch series "kasan: memorize and print call_rcu stack", v8.

This patchset improves KASAN reports by making them to have call_rcu()
call stack information.  It is useful for programmers to solve
use-after-free or double-free memory issue.

The KASAN report was as follows(cleaned up slightly):

BUG: KASAN: use-after-free in kasan_rcu_reclaim+0x58/0x60

Freed by task 0:
 kasan_save_stack+0x24/0x50
 kasan_set_track+0x24/0x38
 kasan_set_free_info+0x18/0x20
 __kasan_slab_free+0x10c/0x170
 kasan_slab_free+0x10/0x18
 kfree+0x98/0x270
 kasan_rcu_reclaim+0x1c/0x60

Last call_rcu():
 kasan_save_stack+0x24/0x50
 kasan_record_aux_stack+0xbc/0xd0
 call_rcu+0x8c/0x580
 kasan_rcu_uaf+0xf4/0xf8

Generic KASAN will record the last two call_rcu() call stacks and print up
to 2 call_rcu() call stacks in KASAN report.  it is only suitable for
generic KASAN.

This feature considers the size of struct kasan_alloc_meta and
kasan_free_meta, we try to optimize the structure layout and size, lets it
get better memory consumption.

[1]https://bugzilla.kernel.org/show_bug.cgi?id=198437
[2]https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack$20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ

This patch (of 4):

This feature will record the last two call_rcu() call stacks and prints up
to 2 call_rcu() call stacks in KASAN report.

When call_rcu() is called, we store the call_rcu() call stack into slub
alloc meta-data, so that the KASAN report can print rcu stack.

[1]https://bugzilla.kernel.org/show_bug.cgi?id=198437
[2]https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack$20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ

[walter-zh.wu@mediatek.com: build fix]
  Link: http://lkml.kernel.org/r/20200710162401.23816-1-walter-zh.wu@mediatek.com

Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Link: http://lkml.kernel.org/r/20200710162123.23713-1-walter-zh.wu@mediatek.com
Link: http://lkml.kernel.org/r/20200601050847.1096-1-walter-zh.wu@mediatek.com
Link: http://lkml.kernel.org/r/20200601050927.1153-1-walter-zh.wu@mediatek.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 23 insertions, 5 deletions

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 51ec45407a0b..445a9d56eb13 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -106,15 +106,20 @@ static void end_report(unsigned long *flags)
 	kasan_enable_current();
 }
 
+static void print_stack(depot_stack_handle_t stack)
+{
+	unsigned long *entries;
+	unsigned int nr_entries;
+
+	nr_entries = stack_depot_fetch(stack, &entries);
+	stack_trace_print(entries, nr_entries, 0);
+}
+
 static void print_track(struct kasan_track *track, const char *prefix)
 {
 	pr_err("%s by task %u:\n", prefix, track->pid);
 	if (track->stack) {
-		unsigned long *entries;
-		unsigned int nr_entries;
-
-		nr_entries = stack_depot_fetch(track->stack, &entries);
-		stack_trace_print(entries, nr_entries, 0);
+		print_stack(track->stack);
 	} else {
 		pr_err("(stack is not available)\n");
 	}
@@ -193,6 +198,19 @@ static void describe_object(struct kmem_cache *cache, void *object,
 		free_track = kasan_get_free_track(cache, object, tag);
 		print_track(free_track, "Freed");
 		pr_err("\n");
+
+#ifdef CONFIG_KASAN_GENERIC
+		if (alloc_info->aux_stack[0]) {
+			pr_err("Last call_rcu():\n");
+			print_stack(alloc_info->aux_stack[0]);
+			pr_err("\n");
+		}
+		if (alloc_info->aux_stack[1]) {
+			pr_err("Second to last call_rcu():\n");
+			print_stack(alloc_info->aux_stack[1]);
+			pr_err("\n");
+		}
+#endif
 	}
 
 	describe_object_addr(cache, object, addr);