CVE-2022-50369

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> drm/vkms: Fix null-ptr-deref in vkms_release()<br /> <br /> A null-ptr-deref is triggered when it tries to destroy the workqueue in<br /> vkms-&gt;output.composer_workq in vkms_release().<br /> <br /> KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f]<br /> CPU: 5 PID: 17193 Comm: modprobe Not tainted 6.0.0-11331-gd465bff130bf #24<br /> RIP: 0010:destroy_workqueue+0x2f/0x710<br /> ...<br /> Call Trace:<br /> <br /> ? vkms_config_debugfs_init+0x50/0x50 [vkms]<br /> __devm_drm_dev_alloc+0x15a/0x1c0 [drm]<br /> vkms_init+0x245/0x1000 [vkms]<br /> do_one_initcall+0xd0/0x4f0<br /> do_init_module+0x1a4/0x680<br /> load_module+0x6249/0x7110<br /> __do_sys_finit_module+0x140/0x200<br /> do_syscall_64+0x35/0x80<br /> entry_SYSCALL_64_after_hwframe+0x46/0xb0<br /> <br /> The reason is that an OOM happened which triggers the destroy of the<br /> workqueue, however, the workqueue is alloced in the later process,<br /> thus a null-ptr-deref happened. A simple call graph is shown as below:<br /> <br /> vkms_init()<br /> vkms_create()<br /> devm_drm_dev_alloc()<br /> __devm_drm_dev_alloc()<br /> devm_drm_dev_init()<br /> devm_add_action_or_reset()<br /> devm_add_action() # an error happened<br /> devm_drm_dev_init_release()<br /> drm_dev_put()<br /> kref_put()<br /> drm_dev_release()<br /> vkms_release()<br /> destroy_workqueue() # null-ptr-deref happened<br /> vkms_modeset_init()<br /> vkms_output_init()<br /> vkms_crtc_init() # where the workqueue get allocated<br /> <br /> Fix this by checking if composer_workq is NULL before passing it to<br /> the destroy_workqueue() in vkms_release().