From: Yuan Can yuancan@huawei.com
[ Upstream commit 2fe2a8f40c21161ffe7653cc234e7934db5b7cc5 ]
A null-ptr-deref is triggered when it tries to destroy the workqueue in vkms->output.composer_workq in vkms_release().
KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f] CPU: 5 PID: 17193 Comm: modprobe Not tainted 6.0.0-11331-gd465bff130bf #24 RIP: 0010:destroy_workqueue+0x2f/0x710 ... Call Trace: <TASK> ? vkms_config_debugfs_init+0x50/0x50 [vkms] __devm_drm_dev_alloc+0x15a/0x1c0 [drm] vkms_init+0x245/0x1000 [vkms] do_one_initcall+0xd0/0x4f0 do_init_module+0x1a4/0x680 load_module+0x6249/0x7110 __do_sys_finit_module+0x140/0x200 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0
The reason is that an OOM happened which triggers the destroy of the workqueue, however, the workqueue is alloced in the later process, thus a null-ptr-deref happened. A simple call graph is shown as below:
vkms_init() vkms_create() devm_drm_dev_alloc() __devm_drm_dev_alloc() devm_drm_dev_init() devm_add_action_or_reset() devm_add_action() # an error happened devm_drm_dev_init_release() drm_dev_put() kref_put() drm_dev_release() vkms_release() destroy_workqueue() # null-ptr-deref happened vkms_modeset_init() vkms_output_init() vkms_crtc_init() # where the workqueue get allocated
Fix this by checking if composer_workq is NULL before passing it to the destroy_workqueue() in vkms_release().
Fixes: 6c234fe37c57 ("drm/vkms: Implement CRC debugfs API") Signed-off-by: Yuan Can yuancan@huawei.com Reviewed-by: Melissa Wen mwen@igalia.com Signed-off-by: Melissa Wen melissa.srw@gmail.com Link: https://patchwork.freedesktop.org/patch/msgid/20221101065156.41584-3-yuancan... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/vkms/vkms_drv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c index cb0b6230c22ce..838428988f79d 100644 --- a/drivers/gpu/drm/vkms/vkms_drv.c +++ b/drivers/gpu/drm/vkms/vkms_drv.c @@ -61,7 +61,8 @@ static void vkms_release(struct drm_device *dev) { struct vkms_device *vkms = container_of(dev, struct vkms_device, drm);
- destroy_workqueue(vkms->output.composer_workq); + if (vkms->output.composer_workq) + destroy_workqueue(vkms->output.composer_workq); }
static void vkms_atomic_commit_tail(struct drm_atomic_state *old_state)