Two paths through vmw_vkms_init() can leave vmw->crc_workq NULL while
still leaving the rest of the driver in a state that calls
vmw_vkms_cleanup() at module unload:
1. vmw_host_get_guestinfo(GUESTINFO_VBLANK, ...) failing or
returning an oversized buffer -- the common case on hosts
without a VBLANK guestinfo entry -- early-returned before the
workqueue allocation.
2. alloc_ordered_workqueue() returning NULL on memory pressure.
vmw_vkms_cleanup() then calls destroy_workqueue(NULL), which
dereferences wq->name and panics.
Fix the first case by removing the early return: vmw->vkms_enabled
is already false on the rpci-failure path so no work will ever be
queued, and allocating the workqueue unconditionally keeps the
control flow simple. Fix the second case by guarding the cleanup
with a NULL check, since alloc_ordered_workqueue() can still fail
under low memory.
Fixes: 7b0062036c3b ("drm/vmwgfx: Implement virtual crc generation")
Cc: [email protected]
Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Zack Rusin <[email protected]>
---
drivers/gpu/drm/vmwgfx/vmwgfx_vkms.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_vkms.c
b/drivers/gpu/drm/vmwgfx/vmwgfx_vkms.c
index 5abd7f5ad2db..0d499917682d 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_vkms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_vkms.c
@@ -214,14 +214,14 @@ vmw_vkms_init(struct vmw_private *vmw)
vmw->vkms_enabled = false;
ret = vmw_host_get_guestinfo(GUESTINFO_VBLANK, buffer, &buf_len);
- if (ret || buf_len > max_buf_len)
- return;
- buffer[buf_len] = '\0';
+ if (!ret && buf_len <= max_buf_len) {
+ buffer[buf_len] = '\0';
- ret = kstrtobool(buffer, &vmw->vkms_enabled);
- if (!ret && vmw->vkms_enabled) {
- ret = drm_vblank_init(&vmw->drm, VMWGFX_NUM_DISPLAY_UNITS);
- vmw->vkms_enabled = (ret == 0);
+ ret = kstrtobool(buffer, &vmw->vkms_enabled);
+ if (!ret && vmw->vkms_enabled) {
+ ret = drm_vblank_init(&vmw->drm,
VMWGFX_NUM_DISPLAY_UNITS);
+ vmw->vkms_enabled = (ret == 0);
+ }
}
vmw->crc_workq = alloc_ordered_workqueue("vmwgfx_crc_generator", 0);
@@ -236,7 +236,8 @@ vmw_vkms_init(struct vmw_private *vmw)
void
vmw_vkms_cleanup(struct vmw_private *vmw)
{
- destroy_workqueue(vmw->crc_workq);
+ if (vmw->crc_workq)
+ destroy_workqueue(vmw->crc_workq);
}
bool
--
2.51.0
