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From:   Alexander Popov <alex.popov@linux.com>
To:     Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
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        Alexander Popov <alex.popov@linux.com>
Cc:     notify@kernel.org
Subject: [PATCH RFC 2/2] lkdtm: Add heap spraying test
Date:   Thu, 13 Aug 2020 18:19:22 +0300
Message-Id: <20200813151922.1093791-3-alex.popov@linux.com>
In-Reply-To: <20200813151922.1093791-1-alex.popov@linux.com>
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Add a simple test for CONFIG_SLAB_QUARANTINE.

It performs heap spraying that aims to reallocate the recently freed heap
object. This technique is used for exploiting use-after-free
vulnerabilities in the kernel code.

This test shows that CONFIG_SLAB_QUARANTINE breaks heap spraying
exploitation technique.

Signed-off-by: Alexander Popov <alex.popov@linux.com>
---
 drivers/misc/lkdtm/core.c  |  1 +
 drivers/misc/lkdtm/heap.c  | 40 ++++++++++++++++++++++++++++++++++++++
 drivers/misc/lkdtm/lkdtm.h |  1 +
 3 files changed, 42 insertions(+)

diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index a5e344df9166..78b7669c35eb 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -126,6 +126,7 @@ static const struct crashtype crashtypes[] = {
 	CRASHTYPE(SLAB_FREE_DOUBLE),
 	CRASHTYPE(SLAB_FREE_CROSS),
 	CRASHTYPE(SLAB_FREE_PAGE),
+	CRASHTYPE(HEAP_SPRAY),
 	CRASHTYPE(SOFTLOCKUP),
 	CRASHTYPE(HARDLOCKUP),
 	CRASHTYPE(SPINLOCKUP),
diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index 1323bc16f113..a72a241e314a 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -205,6 +205,46 @@ static void ctor_a(void *region)
 static void ctor_b(void *region)
 { }
 
+#define HEAP_SPRAY_SIZE 128
+
+void lkdtm_HEAP_SPRAY(void)
+{
+	int *addr;
+	int *spray_addrs[HEAP_SPRAY_SIZE] = { 0 };
+	unsigned long i = 0;
+
+	addr = kmem_cache_alloc(a_cache, GFP_KERNEL);
+	if (!addr) {
+		pr_info("Unable to allocate memory in lkdtm-heap-a cache\n");
+		return;
+	}
+
+	*addr = 0x31337;
+	kmem_cache_free(a_cache, addr);
+
+	pr_info("Performing heap spraying...\n");
+	for (i = 0; i < HEAP_SPRAY_SIZE; i++) {
+		spray_addrs[i] = kmem_cache_alloc(a_cache, GFP_KERNEL);
+		*spray_addrs[i] = 0x31337;
+		pr_info("attempt %lu: spray alloc addr %p vs freed addr %p\n",
+						i, spray_addrs[i], addr);
+		if (spray_addrs[i] == addr) {
+			pr_info("freed addr is reallocated!\n");
+			break;
+		}
+	}
+
+	if (i < HEAP_SPRAY_SIZE)
+		pr_info("FAIL! Heap spraying succeed :(\n");
+	else
+		pr_info("OK! Heap spraying hasn't succeed :)\n");
+
+	for (i = 0; i < HEAP_SPRAY_SIZE; i++) {
+		if (spray_addrs[i])
+			kmem_cache_free(a_cache, spray_addrs[i]);
+	}
+}
+
 void __init lkdtm_heap_init(void)
 {
 	double_free_cache = kmem_cache_create("lkdtm-heap-double_free",
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index 8878538b2c13..dfafb4ae6f3a 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -45,6 +45,7 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void);
 void lkdtm_SLAB_FREE_DOUBLE(void);
 void lkdtm_SLAB_FREE_CROSS(void);
 void lkdtm_SLAB_FREE_PAGE(void);
+void lkdtm_HEAP_SPRAY(void);
 
 /* lkdtm_perms.c */
 void __init lkdtm_perms_init(void);
-- 
2.26.2