[PATCH AUTOSEL 5.19 28/36] drm/meson: reorder driver deinit sequence to fix use-after-free bug

Sasha Levin
2022-10-10T00:20:13Z

From: Adrián Larumbe <adrian.larumbe@collabora.com>

[ Upstream commit 31c519981eb141c7ec39bfd5be25d35f02edb868 ]

Unloading the driver triggers the following KASAN warning:

[ +0.006275] =============================================================
[ +0.000029] BUG: KASAN: use-after-free in __list_del_entry_valid+0xe0/0x1a0
[ +0.000026] Read of size 8 at addr ffff000020c395e0 by task rmmod/2695

[ +0.000019] CPU: 5 PID: 2695 Comm: rmmod Tainted: G C O 5.19.0-rc6-lrmbkasan+ #1
[ +0.000013] Hardware name: Hardkernel ODROID-N2Plus (DT)
[ +0.000008] Call trace:
[ +0.000007] dump_backtrace+0x1ec/0x280
[ +0.000013] show_stack+0x24/0x80
[ +0.000008] dump_stack_lvl+0x98/0xd4
[ +0.000011] print_address_description.constprop.0+0x80/0x520
[ +0.000011] print_report+0x128/0x260
[ +0.000007] kasan_report+0xb8/0xfc
[ +0.000008] __asan_report_load8_noabort+0x3c/0x50
[ +0.000010] __list_del_entry_valid+0xe0/0x1a0
[ +0.000009] drm_atomic_private_obj_fini+0x30/0x200 [drm]
[ +0.000172] drm_bridge_detach+0x94/0x260 [drm]
[ +0.000145] drm_encoder_cleanup+0xa4/0x290 [drm]
[ +0.000144] drm_mode_config_cleanup+0x118/0x740 [drm]
[ +0.000143] drm_mode_config_init_release+0x1c/0x2c [drm]
[ +0.000144] drm_managed_release+0x170/0x414 [drm]
[ +0.000142] drm_dev_put.part.0+0xc0/0x124 [drm]
[ +0.000143] drm_dev_put+0x20/0x30 [drm]
[ +0.000142] meson_drv_unbind+0x1d8/0x2ac [meson_drm]
[ +0.000028] take_down_aggregate_device+0xb0/0x160
[ +0.000016] component_del+0x18c/0x360
[ +0.000009] meson_dw_hdmi_remove+0x28/0x40 [meson_dw_hdmi]
[ +0.000015] platform_remove+0x64/0xb0
[ +0.000009] device_remove+0xb8/0x154
[ +0.000009] device_release_driver_internal+0x398/0x5b0
[ +0.000009] driver_detach+0xac/0x1b0
[ +0.000009] bus_remove_driver+0x158/0x29c
[ +0.000009] driver_unregister+0x70/0xb0
[ +0.000008] platform_driver_unregister+0x20/0x2c
[ +0.000008] meson_dw_hdmi_platform_driver_exit+0x1c/0x30 [meson_dw_hdmi]
[ +0.000012] __do_sys_delete_module+0x288/0x400
[ +0.000011] __arm64_sys_delete_module+0x5c/0x80
[ +0.000009] invoke_syscall+0x74/0x260
[ +0.000009] el0_svc_common.constprop.0+0xcc/0x260
[ +0.000009] do_el0_svc+0x50/0x70
[ +0.000007] el0_svc+0x68/0x1a0
[ +0.000012] el0t_64_sync_handler+0x11c/0x150
[ +0.000008] el0t_64_sync+0x18c/0x190

[ +0.000018] Allocated by task 0:
[ +0.000007] (stack is not available)

[ +0.000011] Freed by task 2695:
[ +0.000008] kasan_save_stack+0x2c/0x5c
[ +0.000011] kasan_set_track+0x2c/0x40
[ +0.000008] kasan_set_free_info+0x28/0x50
[ +0.000009] ____kasan_slab_free+0x128/0x1d4
[ +0.000008] __kasan_slab_free+0x18/0x24
[ +0.000007] slab_free_freelist_hook+0x108/0x230
[ +0.000011] kfree+0x110/0x35c
[ +0.000008] release_nodes+0xf0/0x16c
[ +0.000009] devres_release_group+0x180/0x270
[ +0.000008] component_unbind+0x128/0x1e0
[ +0.000010] component_unbind_all+0x1b8/0x264
[ +0.000009] meson_drv_unbind+0x1a0/0x2ac [meson_drm]
[ +0.000025] take_down_aggregate_device+0xb0/0x160
[ +0.000009] component_del+0x18c/0x360
[ +0.000009] meson_dw_hdmi_remove+0x28/0x40 [meson_dw_hdmi]
[ +0.000012] platform_remove+0x64/0xb0
[ +0.000008] device_remove+0xb8/0x154
[ +0.000009] device_release_driver_internal+0x398/0x5b0
[ +0.000009] driver_detach+0xac/0x1b0
[ +0.000009] bus_remove_driver+0x158/0x29c
[ +0.000008] driver_unregister+0x70/0xb0
[ +0.000008] platform_driver_unregister+0x20/0x2c
[ +0.000008] meson_dw_hdmi_platform_driver_exit+0x1c/0x30 [meson_dw_hdmi]
[ +0.000011] __do_sys_delete_module+0x288/0x400
[ +0.000010] __arm64_sys_delete_module+0x5c/0x80
[ +0.000008] invoke_syscall+0x74/0x260
[ +0.000008] el0_svc_common.constprop.0+0xcc/0x260
[ +0.000008] do_el0_svc+0x50/0x70
[ +0.000007] el0_svc+0x68/0x1a0
[ +0.000009] el0t_64_sync_handler+0x11c/0x150
[ +0.000009] el0t_64_sync+0x18c/0x190

[ +0.000014] The buggy address belongs to the object at ffff000020c39000
which belongs to the cache kmalloc-4k of size 4096
[ +0.000008] The buggy address is located 1504 bytes inside of
4096-byte region [ffff000020c39000, ffff000020c3a000)

[ +0.000016] The buggy address belongs to the physical page:
[ +0.000009] page:fffffc0000830e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x20c38
[ +0.000013] head:fffffc0000830e00 order:3 compound_mapcount:0 compound_pincount:0
[ +0.000008] flags: 0xffff00000010200(slab|head|node=0|zone=0|lastcpupid=0xffff)
[ +0.000019] raw: 0ffff00000010200 fffffc0000fd4808 fffffc0000126208 ffff000000002e80
[ +0.000009] raw: 0000000000000000 0000000000020002 00000001ffffffff 0000000000000000
[ +0.000008] page dumped because: kasan: bad access detected

[ +0.000011] Memory state around the buggy address:
[ +0.000008] ffff000020c39480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ +0.000007] ffff000020c39500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ +0.000007] >ffff000020c39580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ +0.000007] ^
[ +0.000007] ffff000020c39600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ +0.000007] ffff000020c39680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ +0.000006] ==================================================================

The reason this is happening is unloading meson-dw-hdmi will cause the
component API to take down the aggregate device, which in turn will cause
all devres-managed memory to be freed, including the struct dw_hdmi
allocated in dw_hdmi_probe. This struct embeds a struct drm_bridge that is
added at the end of the function, and which is later on picked up in
meson_encoder_hdmi_init.

However, when attaching the bridge to the encoder created in
meson_encoder_hdmi_init, it's linked to the encoder's bridge chain, from
where it never leaves, even after devres_release_group is called when the
driver's components are unbound and the embedding structure freed.

Then, when calling drm_dev_put in the aggregate driver's unbind function,
drm_bridge_detach is called for every single bridge linked to the encoder,
including the one whose memory had already been deallocated.

Fix by calling component_unbind_all after drm_dev_put.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220919010940.419893-2-adrian.larumbe@collabora.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/meson/meson_drv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c
index bd4ca11d3ff5..7df149d42728 100644
--- a/drivers/gpu/drm/meson/meson_drv.c
+++ b/drivers/gpu/drm/meson/meson_drv.c
@@ -388,9 +388,9 @@ static void meson_drv_unbind(struct device *dev)
drm_dev_unregister(drm);
drm_kms_helper_poll_fini(drm);
drm_atomic_helper_shutdown(drm);
- component_unbind_all(dev, drm);
free_irq(priv->vsync_irq, drm);
drm_dev_put(drm);
+ component_unbind_all(dev, drm);

if (priv->afbcd.ops)
priv->afbcd.ops->exit(priv);
--
2.35.1