[PATCH 3/3] drm/tests: Fix a use-after-free bug in __drm_kunit_helper_alloc_drm_device()

[Arthur Grillo]

In __drm_kunit_helper_alloc_drm_device_with_driver(), a drm_driver is
allocated with kunit_kzalloc. If the dev argument was allocated by
drm_kunit_helper_alloc_device, its deferred actions would access the
already deallocated drm_driver.

To fix that, move the deferred to the top of the resource stack.

==================================================================
BUG: KASAN: slab-use-after-free in devm_drm_dev_init_release+0x54/0xb0
Read of size 8 at addr 0000000063194e28 by task kunit_try_catch/127

CPU: 0 PID: 127 Comm: kunit_try_catch Tainted: G        W        N 6.5.0-rc2-00620-g4f77e58c6017 #35
Stack:
 606c9a22 606c9a22 00000000 606c9a22
 6056b8fe 63033b10 00000000 60040850
 63033a80 60574ca4 60574c4a 63033b10
Call Trace:
 [<600295a2>] show_stack+0x202/0x220
 [<6056b8fe>] ? _printk+0x0/0x78
 [<60040850>] ? um_set_signals+0x0/0x40
 [<60574ca4>] dump_stack_lvl+0x5a/0x6b
 [<60574c4a>] ? dump_stack_lvl+0x0/0x6b
 [<6019d40d>] print_report+0x1bd/0x670
 [<6056b96b>] ? _printk+0x6d/0x78
 [<6056b8fe>] ? _printk+0x0/0x78
 [<6019f0e6>] ? kasan_complete_mode_report_info+0x116/0x180
 [<603d16d4>] ? devm_drm_dev_init_release+0x54/0xb0
 [<6019db14>] kasan_report+0x184/0x1b0
 [<603d16d4>] ? devm_drm_dev_init_release+0x54/0xb0
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6019e7ec>] __asan_load8+0x7c/0x80
 [<603d16d4>] devm_drm_dev_init_release+0x54/0xb0
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<603d1680>] ? devm_drm_dev_init_release+0x0/0xb0
 [<604b0bde>] devm_action_release+0x2e/0x40
 [<604afd60>] devres_release_all+0x100/0x170
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<604a7f7d>] device_release_driver_internal+0x39d/0x510
 [<6027d7f0>] ? sysfs_remove_link+0x0/0x50
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<604a8104>] device_release_driver+0x14/0x20
 [<604a3592>] bus_remove_device+0x1e2/0x200
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6049de5a>] device_del+0x3ba/0x850
 [<6019f790>] ? kasan_quarantine_put+0x0/0x170
 [<60137bad>] ? kfree+0x5d/0x80
 [<6019e7f0>] ? __asan_store8+0x0/0x90
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<604475a0>] ? kunit_action_platform_device_del+0x0/0x20
 [<604ad4b0>] platform_device_del+0x40/0x140
 [<601957f3>] ? __kmem_cache_free+0xc3/0x230
 [<6019e7f0>] ? __asan_store8+0x0/0x90
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<604475a0>] ? kunit_action_platform_device_del+0x0/0x20
 [<604475b0>] kunit_action_platform_device_del+0x10/0x20
 [<6031bf80>] __kunit_action_free+0x30/0x40
 [<6031bf50>] ? __kunit_action_free+0x0/0x40
 [<6031bae4>] kunit_remove_resource+0xf4/0x150
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<60040850>] ? um_set_signals+0x0/0x40
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6031b396>] kunit_cleanup+0xb6/0x140
 [<605848cd>] ? __schedule+0x6bd/0x7a0
 [<6019e7f0>] ? __asan_store8+0x0/0x90
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6031b715>] kunit_try_run_case_cleanup+0x95/0xb0
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<6031b680>] ? kunit_try_run_case_cleanup+0x0/0xb0
 [<6031e240>] kunit_generic_run_threadfn_adapter+0x30/0x60
 [<6008d15e>] kthread+0x28e/0x2e0
 [<6031e210>] ? kunit_generic_run_threadfn_adapter+0x0/0x60
 [<6019e7f0>] ? __asan_store8+0x0/0x90
 [<6008ced0>] ? kthread+0x0/0x2e0
 [<6019e770>] ? __asan_load8+0x0/0x80
 [<600270e6>] new_thread_handler+0x136/0x1a0

Allocated by task 126:
 save_stack_trace+0x5b/0x70
 stack_trace_save+0x7a/0xa0
 kasan_set_track+0x6c/0xa0
 kasan_save_alloc_info+0x26/0x30
 __kasan_kmalloc+0x91/0xa0
 __kmalloc+0xb9/0x110
 kunit_kmalloc_array+0x23/0x60
 drm_test_fb_build_fourcc_list+0x8b/0x390
 kunit_try_run_case+0xab/0x140
 kunit_generic_run_threadfn_adapter+0x30/0x60
 kthread+0x28e/0x2e0
 new_thread_handler+0x136/0x1a0

Freed by task 127:
 save_stack_trace+0x5b/0x70
 stack_trace_save+0x7a/0xa0
 kasan_set_track+0x6c/0xa0
 kasan_save_free_info+0x30/0x50
 ____kasan_slab_free+0x12c/0x190
 __kasan_slab_free+0x18/0x20
 __kmem_cache_free+0xc3/0x230
 kfree+0x5d/0x80
 __kunit_action_free+0x30/0x40
 kunit_remove_resource+0xf4/0x150
 kunit_cleanup+0xb6/0x140
 kunit_try_run_case_cleanup+0x95/0xb0
 kunit_generic_run_threadfn_adapter+0x30/0x60
 kthread+0x28e/0x2e0
 new_thread_handler+0x136/0x1a0

The buggy address belongs to the object at 0000000063194e00
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 40 bytes inside of
 freed 256-byte region [0000000063194e00, 0000000063194f00)

The buggy address belongs to the physical page:
page:00000000d99927cc refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3194
flags: 0x200(slab|zone=0)
page_type: 0xffffffff()
raw: 0000000000000200 0000000062401900 0000000000000122 0000000000000000
raw: 0000000000000000 0000000080080008 00000001ffffffff
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 0000000063194d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 0000000063194d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>0000000063194e00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 0000000063194e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 0000000063194f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Signed-off-by: Arthur Grillo <arthurgrillo at riseup.net>
---
 drivers/gpu/drm/tests/drm_kunit_helpers.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/tests/drm_kunit_helpers.c b/drivers/gpu/drm/tests/drm_kunit_helpers.c
index 3150dbc647ee..655cedf7ab13 100644
--- a/drivers/gpu/drm/tests/drm_kunit_helpers.c
+++ b/drivers/gpu/drm/tests/drm_kunit_helpers.c
@@ -129,6 +129,7 @@ __drm_kunit_helper_alloc_drm_device_with_driver(struct kunit *test,
 						const struct drm_driver *driver)
 {
 	struct drm_device *drm;
+	struct platform_device *pdev = to_platform_device(dev);
 	void *container;
 	int ret;
 
@@ -143,6 +144,21 @@ __drm_kunit_helper_alloc_drm_device_with_driver(struct kunit *test,
 	if (ret)
 		return ERR_PTR(ret);
 
+	ret = kunit_move_action_to_top_or_reset(test,
+						kunit_action_platform_driver_unregister,
+						&fake_platform_driver);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = kunit_move_action_to_top_or_reset(test,
+						kunit_action_platform_device_put,
+						pdev);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = kunit_move_action_to_top_or_reset(test,
+						kunit_action_platform_device_del,
+						pdev);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
 	return drm;
 }
 EXPORT_SYMBOL_GPL(__drm_kunit_helper_alloc_drm_device_with_driver);

-- 
2.41.0