CVE-2022-50378

In the Linux kernel, the following vulnerability has been resolved:

drm/meson: reorder driver deinit sequence to fix use-after-free bug

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 —truncated—

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/31c519981eb141c7ec39bfd5be25d35f02edb868
• https://git.kernel.org/stable/c/9190d287f7a6b02b50b510045b0edf448ed68e88
• https://git.kernel.org/stable/c/9d33348513c36337f91f1991da23f41514d4de39
• https://git.kernel.org/stable/c/d76ff04a72f90767455059c8239b06042cd0ed23