This is a note to let you know that I've just added the patch titled
drm/vkms: Fix null-ptr-deref in vkms_release()
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-vkms-fix-null-ptr-deref-in-vkms_release.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2c00a62b4b040a52adb37cd1bf3a8e35259041c0
Author: Yuan Can <yuancan@xxxxxxxxxx>
Date: Tue Nov 1 06:51:56 2022 +0000
drm/vkms: Fix null-ptr-deref in vkms_release()
[ 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@xxxxxxxxxx>
Reviewed-by: Melissa Wen <mwen@xxxxxxxxxx>
Signed-off-by: Melissa Wen <melissa.srw@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20221101065156.41584-3-yuancan@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index dfe983eaa07ff..f716c5796f5fc 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -57,7 +57,8 @@ static void vkms_release(struct drm_device *dev)
{
struct vkms_device *vkms = drm_device_to_vkms_device(dev);
- 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)
