linux-kernel - [PATCH 3/5] kmemleak: account for tagged pointers when calculating pointer range

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Date:   Mon, 11 Feb 2019 22:59:52 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Qian Cai <cai@....pw>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH 3/5] kmemleak: account for tagged pointers when calculating pointer range

kmemleak keeps two global variables, min_addr and max_addr, which store
the range of valid (encountered by kmemleak) pointer values, which it
later uses to speed up pointer lookup when scanning blocks.

With tagged pointers this range will get bigger than it needs to be.
This patch makes kmemleak untag pointers before saving them to min_addr
and max_addr and when performing a lookup.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 mm/kmemleak.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index f9d9dc250428..707fa5579f66 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -574,6 +574,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
 	unsigned long flags;
 	struct kmemleak_object *object, *parent;
 	struct rb_node **link, *rb_parent;
+	unsigned long untagged_ptr;
 
 	object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
 	if (!object) {
@@ -619,8 +620,9 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
 
 	write_lock_irqsave(&kmemleak_lock, flags);
 
-	min_addr = min(min_addr, ptr);
-	max_addr = max(max_addr, ptr + size);
+	untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr);
+	min_addr = min(min_addr, untagged_ptr);
+	max_addr = max(max_addr, untagged_ptr + size);
 	link = &object_tree_root.rb_node;
 	rb_parent = NULL;
 	while (*link) {
@@ -1333,6 +1335,7 @@ static void scan_block(void *_start, void *_end,
 	unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
 	unsigned long *end = _end - (BYTES_PER_POINTER - 1);
 	unsigned long flags;
+	unsigned long untagged_ptr;
 
 	read_lock_irqsave(&kmemleak_lock, flags);
 	for (ptr = start; ptr < end; ptr++) {
@@ -1347,7 +1350,8 @@ static void scan_block(void *_start, void *_end,
 		pointer = *ptr;
 		kasan_enable_current();
 
-		if (pointer < min_addr || pointer >= max_addr)
+		untagged_ptr = (unsigned long)kasan_reset_tag((void *)pointer);
+		if (untagged_ptr < min_addr || untagged_ptr >= max_addr)
 			continue;
 
 		/*
-- 
2.20.1.791.gb4d0f1c61a-goog