| Message ID | 20230905085832.2103-2-thomas.hellstrom@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/drm_exec, drm/drm_kunit: Fix / WA for uaf and lock alloc tracking. | expand |
On Tue, Sep 05, 2023 at 10:58:30AM +0200, Thomas Hellström wrote: > when using __drm_kunit_helper_alloc_drm_device() the driver may be > dereferenced by device-managed resources up until the device is > freed, which is typically later than the kunit-managed resource code > frees it. I'd like to have a bit more context on how a driver can end up in that situation? Maxime
Hi maxime, On 9/5/23 14:06, Maxime Ripard wrote: > On Tue, Sep 05, 2023 at 10:58:30AM +0200, Thomas Hellström wrote: >> when using __drm_kunit_helper_alloc_drm_device() the driver may be >> dereferenced by device-managed resources up until the device is >> freed, which is typically later than the kunit-managed resource code >> frees it. > I'd like to have a bit more context on how a driver can end up in that > situation? I interpret the attached traces as follows. INIT: Code allocates a struct device as a kunit-managed resource. Code allocates a drm driver as a kunit-managed resource. Code allocates a drm device as a device-managed resource. EXIT: Kunit resource cleanup frees the drm driver Kunit resource cleanup frees the struct device, which starts a device-managed resource cleanup device-managed cleanup calls drm_dev_put() drm_dev_put() dereferences the (now freed) drm driver -> Boom. It should be sufficient to enable KASAN and run the drm_exec_test kunit test to trigger this. Thanks, Thomas > > Maxime
On Tue, Sep 05, 2023 at 02:43:00PM +0200, Thomas Hellström wrote: > Hi maxime, > > On 9/5/23 14:06, Maxime Ripard wrote: > > On Tue, Sep 05, 2023 at 10:58:30AM +0200, Thomas Hellström wrote: > > > when using __drm_kunit_helper_alloc_drm_device() the driver may be > > > dereferenced by device-managed resources up until the device is > > > freed, which is typically later than the kunit-managed resource code > > > frees it. > > I'd like to have a bit more context on how a driver can end up in that > > situation? > > I interpret the attached traces as follows. > > INIT: > > Code allocates a struct device as a kunit-managed resource. > Code allocates a drm driver as a kunit-managed resource. > Code allocates a drm device as a device-managed resource. > > EXIT: > > Kunit resource cleanup frees the drm driver > Kunit resource cleanup frees the struct device, which starts a > device-managed resource cleanup > device-managed cleanup calls drm_dev_put() > drm_dev_put() dereferences the (now freed) drm driver -> Boom. > > It should be sufficient to enable KASAN and run the drm_exec_test kunit test > to trigger this. Ack. Can you put this into your commit log? Thanks! Maxime
Hi, Maxime, On 9/6/23 12:08, Maxime Ripard wrote: > On Tue, Sep 05, 2023 at 02:43:00PM +0200, Thomas Hellström wrote: >> Hi maxime, >> >> On 9/5/23 14:06, Maxime Ripard wrote: >>> On Tue, Sep 05, 2023 at 10:58:30AM +0200, Thomas Hellström wrote: >>>> when using __drm_kunit_helper_alloc_drm_device() the driver may be >>>> dereferenced by device-managed resources up until the device is >>>> freed, which is typically later than the kunit-managed resource code >>>> frees it. >>> I'd like to have a bit more context on how a driver can end up in that >>> situation? >> I interpret the attached traces as follows. >> >> INIT: >> >> Code allocates a struct device as a kunit-managed resource. >> Code allocates a drm driver as a kunit-managed resource. >> Code allocates a drm device as a device-managed resource. >> >> EXIT: >> >> Kunit resource cleanup frees the drm driver >> Kunit resource cleanup frees the struct device, which starts a >> device-managed resource cleanup >> device-managed cleanup calls drm_dev_put() >> drm_dev_put() dereferences the (now freed) drm driver -> Boom. >> >> It should be sufficient to enable KASAN and run the drm_exec_test kunit test >> to trigger this. > Ack. Can you put this into your commit log? > > Thanks! > Maxime Thanks for reviewing. I'll update this and the other patch with your comments. Thanks, Thomas
diff --git a/include/drm/drm_kunit_helpers.h b/include/drm/drm_kunit_helpers.h index 514c8a7a32f0..ba483c87f0e7 100644 --- a/include/drm/drm_kunit_helpers.h +++ b/include/drm/drm_kunit_helpers.h @@ -3,6 +3,8 @@ #ifndef DRM_KUNIT_HELPERS_H_ #define DRM_KUNIT_HELPERS_H_ +#include <linux/device.h> + #include <kunit/test.h> struct drm_device; @@ -51,7 +53,7 @@ __drm_kunit_helper_alloc_drm_device(struct kunit *test, { struct drm_driver *driver; - driver = kunit_kzalloc(test, sizeof(*driver), GFP_KERNEL); + driver = devm_kzalloc(dev, sizeof(*driver), GFP_KERNEL); KUNIT_ASSERT_NOT_NULL(test, driver); driver->driver_features = features;
when using __drm_kunit_helper_alloc_drm_device() the driver may be dereferenced by device-managed resources up until the device is freed, which is typically later than the kunit-managed resource code frees it. Fix this by simply make the driver device-managed as well. Related KASAN message: [55272.551542] ================================================================== [55272.551551] BUG: KASAN: slab-use-after-free in drm_dev_put.part.0+0xd4/0xe0 [drm] [55272.551603] Read of size 8 at addr ffff888127502828 by task kunit_try_catch/10353 [55272.551612] CPU: 4 PID: 10353 Comm: kunit_try_catch Tainted: G U N 6.5.0-rc7+ #155 [55272.551620] Hardware name: ASUS System Product Name/PRIME B560M-A AC, BIOS 0403 01/26/2021 [55272.551626] Call Trace: [55272.551629] <TASK> [55272.551633] dump_stack_lvl+0x57/0x90 [55272.551639] print_report+0xcf/0x630 [55272.551645] ? _raw_spin_lock_irqsave+0x5f/0x70 [55272.551652] ? drm_dev_put.part.0+0xd4/0xe0 [drm] [55272.551694] kasan_report+0xd7/0x110 [55272.551699] ? drm_dev_put.part.0+0xd4/0xe0 [drm] [55272.551742] drm_dev_put.part.0+0xd4/0xe0 [drm] [55272.551783] devres_release_all+0x15d/0x1f0 [55272.551790] ? __pfx_devres_release_all+0x10/0x10 [55272.551797] device_unbind_cleanup+0x16/0x1a0 [55272.551802] device_release_driver_internal+0x3e5/0x540 [55272.551808] ? kobject_put+0x5d/0x4b0 [55272.551814] bus_remove_device+0x1f1/0x3f0 [55272.551819] device_del+0x342/0x910 [55272.551826] ? __pfx_device_del+0x10/0x10 [55272.551830] ? lock_release+0x339/0x5e0 [55272.551836] ? kunit_remove_resource+0x128/0x290 [kunit] [55272.551845] ? __pfx_lock_release+0x10/0x10 [55272.551851] platform_device_del.part.0+0x1f/0x1e0 [55272.551856] ? _raw_spin_unlock_irqrestore+0x30/0x60 [55272.551863] kunit_remove_resource+0x195/0x290 [kunit] [55272.551871] ? _raw_spin_unlock_irqrestore+0x30/0x60 [55272.551877] kunit_cleanup+0x78/0x120 [kunit] [55272.551885] ? __kthread_parkme+0xc1/0x1f0 [55272.551891] ? __pfx_kunit_try_run_case_cleanup+0x10/0x10 [kunit] [55272.551900] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [kunit] [55272.551909] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit] [55272.551919] kthread+0x2e7/0x3c0 [55272.551924] ? __pfx_kthread+0x10/0x10 [55272.551929] ret_from_fork+0x2d/0x70 [55272.551935] ? __pfx_kthread+0x10/0x10 [55272.551940] ret_from_fork_asm+0x1b/0x30 [55272.551948] </TASK> [55272.551953] Allocated by task 10351: [55272.551956] kasan_save_stack+0x1c/0x40 [55272.551962] kasan_set_track+0x21/0x30 [55272.551966] __kasan_kmalloc+0x8b/0x90 [55272.551970] __kmalloc+0x5e/0x160 [55272.551976] kunit_kmalloc_array+0x1c/0x50 [kunit] [55272.551984] drm_exec_test_init+0xfa/0x2c0 [drm_exec_test] [55272.551991] kunit_try_run_case+0xdd/0x250 [kunit] [55272.551999] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit] [55272.552008] kthread+0x2e7/0x3c0 [55272.552012] ret_from_fork+0x2d/0x70 [55272.552017] ret_from_fork_asm+0x1b/0x30 [55272.552024] Freed by task 10353: [55272.552027] kasan_save_stack+0x1c/0x40 [55272.552032] kasan_set_track+0x21/0x30 [55272.552036] kasan_save_free_info+0x27/0x40 [55272.552041] __kasan_slab_free+0x106/0x180 [55272.552046] slab_free_freelist_hook+0xb3/0x160 [55272.552051] __kmem_cache_free+0xb2/0x290 [55272.552056] kunit_remove_resource+0x195/0x290 [kunit] [55272.552064] kunit_cleanup+0x78/0x120 [kunit] [55272.552072] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit] [55272.552080] kthread+0x2e7/0x3c0 [55272.552085] ret_from_fork+0x2d/0x70 [55272.552089] ret_from_fork_asm+0x1b/0x30 [55272.552096] The buggy address belongs to the object at ffff888127502800 which belongs to the cache kmalloc-512 of size 512 [55272.552105] The buggy address is located 40 bytes inside of freed 512-byte region [ffff888127502800, ffff888127502a00) [55272.552115] The buggy address belongs to the physical page: [55272.552119] page:00000000af6c70ff refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x127500 [55272.552127] head:00000000af6c70ff order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [55272.552133] anon flags: 0x17ffffc0010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff) [55272.552141] page_type: 0xffffffff() [55272.552145] raw: 0017ffffc0010200 ffff888100042c80 0000000000000000 dead000000000001 [55272.552152] raw: 0000000000000000 0000000080200020 00000001ffffffff 0000000000000000 [55272.552157] page dumped because: kasan: bad access detected [55272.552163] Memory state around the buggy address: [55272.552167] ffff888127502700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [55272.552173] ffff888127502780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [55272.552178] >ffff888127502800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [55272.552184] ^ [55272.552187] ffff888127502880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [55272.552193] ffff888127502900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [55272.552198] ================================================================== [55272.552203] Disabling lock debugging due to kernel taint Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: David Airlie <airlied@gmail.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: dri-devel@lists.freedesktop.org Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> --- include/drm/drm_kunit_helpers.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)