Fri, Jul 10, 2026 at 09:36:25PM +0200, ivecera@redhat.com wrote:

When a dpll_pin is shared across multiple dpll_device instances and
those devices are being unregistered (e.g. during driver module removal),
a NULL pointer dereference can occur in dpll_msg_add_pin_ref_sync().

This happens under the following conditions:
- A pin is registered with two or more dpll devices (dpll_A, dpll_B)
- The pin has ref_sync pairs with other pins
- During unregistration of dpll_A's pins, a ref_sync partner pin is
  unregistered first, removing it from dpll_A->pin_refs
- But since the partner pin is still registered with dpll_B, its
  dpll_refs is not empty, so dpll_pin_ref_sync_pair_del() does NOT
  run and the partner stays in the pin's ref_sync_pins xarray
- When the pin itself is then unregistered from dpll_A, the delete
  notification calls dpll_msg_add_pin_ref_sync() which finds the
  partner in ref_sync_pins, passes dpll_pin_available() (partner is
  still registered with dpll_B), but dpll_pin_on_dpll_priv(dpll_A,
  partner) returns NULL because partner was already removed from
  dpll_A->pin_refs
- The NULL priv pointer is passed to the driver's ref_sync_get
  callback, which dereferences it

BUG: kernel NULL pointer dereference, address: 0000000000000034
Oops: Oops: 0000 [#1] SMP NOPTI
RIP: 0010:zl3073x_dpll_input_pin_ref_sync_get+0x73/0x80 [zl3073x]
Call Trace:
 dpll_msg_add_pin_ref_sync+0xb8/0x200
 dpll_cmd_pin_get_one+0x3b6/0x4b0
 dpll_pin_event_send+0x72/0x140
 __dpll_pin_unregister+0x5a/0x2b0
 dpll_pin_unregister+0x49/0x70

Fix this by skipping ref_sync pins whose priv pointer cannot be resolved
for the current dpll device.

Fixes: 58256a26bfb3 ("dpll: add reference sync get/set")
Signed-off-by: Ivan Vecera <ivecera@redhat.com>

Reviewed-by: Jiri Pirko <redacted>