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 [[email protected]: build fix] Link: http://lkml.kernel.org/r/[email protected] Suggested-by: Dmitry Vyukov <[email protected]> Signed-off-by: Walter Wu <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Tested-by: Dmitry Vyukov <[email protected]> Reviewed-by: Dmitry Vyukov <[email protected]> Reviewed-by: Andrey Konovalov <[email protected]> Acked-by: Paul E. McKenney <[email protected]> Cc: Andrey Ryabinin <[email protected]> Cc: Alexander Potapenko <[email protected]> Cc: Josh Triplett <[email protected]> Cc: Mathieu Desnoyers <[email protected]> Cc: Lai Jiangshan <[email protected]> Cc: Joel Fernandes <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Matthias Brugger <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Link: http://lkml.kernel.org/r/[email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Linus Torvalds <[email protected]>
vieko · Aug 7, 2020 · 26e760c · 26e760c
1 parent ac4766b
commit 26e760c
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Showing 6 changed files with 59 additions and 7 deletions.
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
@@ -174,11 +174,13 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
 
 void kasan_cache_shrink(struct kmem_cache *cache);
 void kasan_cache_shutdown(struct kmem_cache *cache);
+void kasan_record_aux_stack(void *ptr);
 
 #else /* CONFIG_KASAN_GENERIC */
 
 static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
 static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
+static inline void kasan_record_aux_stack(void *ptr) {}
 
 #endif /* CONFIG_KASAN_GENERIC */
 

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
@@ -59,6 +59,7 @@
 #include <linux/sched/clock.h>
 #include <linux/vmalloc.h>
 #include <linux/mm.h>
+#include <linux/kasan.h>
 #include "../time/tick-internal.h"
 
 #include "tree.h"
@@ -2890,6 +2891,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
 	head->func = func;
 	head->next = NULL;
 	local_irq_save(flags);
+	kasan_record_aux_stack(head);
 	rdp = this_cpu_ptr(&rcu_data);
 
 	/* Add the callback to our list. */

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
@@ -40,7 +40,7 @@
 #include "kasan.h"
 #include "../slab.h"
 
-static inline depot_stack_handle_t save_stack(gfp_t flags)
+depot_stack_handle_t kasan_save_stack(gfp_t flags)
 {
 	unsigned long entries[KASAN_STACK_DEPTH];
 	unsigned int nr_entries;
@@ -53,7 +53,7 @@ static inline depot_stack_handle_t save_stack(gfp_t flags)
 static inline void set_track(struct kasan_track *track, gfp_t flags)
 {
 	track->pid = current->pid;
-	track->stack = save_stack(flags);
+	track->stack = kasan_save_stack(flags);
 }
 
 void kasan_enable_current(void)

diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
@@ -324,3 +324,24 @@ DEFINE_ASAN_SET_SHADOW(f2);
 DEFINE_ASAN_SET_SHADOW(f3);
 DEFINE_ASAN_SET_SHADOW(f5);
 DEFINE_ASAN_SET_SHADOW(f8);
+
+void kasan_record_aux_stack(void *addr)
+{
+	struct page *page = kasan_addr_to_page(addr);
+	struct kmem_cache *cache;
+	struct kasan_alloc_meta *alloc_info;
+	void *object;
+
+	if (!(page && PageSlab(page)))
+		return;
+
+	cache = page->slab_cache;
+	object = nearest_obj(cache, page, addr);
+	alloc_info = get_alloc_info(cache, object);
+
+	/*
+	 * record the last two call_rcu() call stacks.
+	 */
+	alloc_info->aux_stack[1] = alloc_info->aux_stack[0];
+	alloc_info->aux_stack[0] = kasan_save_stack(GFP_NOWAIT);
+}
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
@@ -104,6 +104,13 @@ struct kasan_track {
 
 struct kasan_alloc_meta {
 	struct kasan_track alloc_track;
+#ifdef CONFIG_KASAN_GENERIC
+	/*
+	 * call_rcu() call stack is stored into struct kasan_alloc_meta.
+	 * The free stack is stored into struct kasan_free_meta.
+	 */
+	depot_stack_handle_t aux_stack[2];
+#endif
 	struct kasan_track free_track[KASAN_NR_FREE_STACKS];
 #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
 	u8 free_pointer_tag[KASAN_NR_FREE_STACKS];
@@ -159,6 +166,8 @@ void kasan_report_invalid_free(void *object, unsigned long ip);
 
 struct page *kasan_addr_to_page(const void *addr);
 
+depot_stack_handle_t kasan_save_stack(gfp_t flags);
+
 #if defined(CONFIG_KASAN_GENERIC) && \
 	(defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
 void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);

diff --git 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);