Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
On Tue, 2022-11-01 at 15:07 +0800, Shang XiaoJing wrote:
> drm_vblank_init() call drmm_add_action_or_reset() with
> drm_vblank_init_release() as action. If __drmm_add_action() failed, will
> directly call drm_vblank_init_release() with the vblank whose worker is
> NULL. As the resule, a null-ptr-deref will happen in
> kthread_destroy_worker(). Add the NULL check before calling
> drm_vblank_destroy_worker().
>
> BUG: null-ptr-deref
> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
> CPU: 5 PID: 961 Comm: modprobe Not tainted 6.0.0-11331-gd465bff130bf-dirty
> RIP: 0010:kthread_destroy_worker+0x25/0xb0
> Call Trace:
> <TASK>
> drm_vblank_init_release+0x124/0x220 [drm]
> ? drm_crtc_vblank_restore+0x8b0/0x8b0 [drm]
> __drmm_add_action_or_reset+0x41/0x50 [drm]
> drm_vblank_init+0x282/0x310 [drm]
> vkms_init+0x35f/0x1000 [vkms]
> ? 0xffffffffc4508000
> ? lock_is_held_type+0xd7/0x130
> ? __kmem_cache_alloc_node+0x1c2/0x2b0
> ? lock_is_held_type+0xd7/0x130
> ? 0xffffffffc4508000
> do_one_initcall+0xd0/0x4f0
> ...
> do_syscall_64+0x35/0x80
> entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
> Fixes: 5e6c2b4f9161 ("drm/vblank: Add vblank works")
> Signed-off-by: Shang XiaoJing <shangxiaojing@xxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_internal.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
> index 7bb98e6a446d..5ea5e260118c 100644
> --- a/drivers/gpu/drm/drm_internal.h
> +++ b/drivers/gpu/drm/drm_internal.h
> @@ -104,7 +104,8 @@ static inline void drm_vblank_flush_worker(struct drm_vblank_crtc *vblank)
>
> static inline void drm_vblank_destroy_worker(struct drm_vblank_crtc *vblank)
> {
> - kthread_destroy_worker(vblank->worker);
> + if (vblank->worker)
> + kthread_destroy_worker(vblank->worker);
> }
>
> int drm_vblank_worker_init(struct drm_vblank_crtc *vblank);
--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat
