Re: [PATCH net] dpll: fix NULL pointer dereference in dpll_msg_add_pin_ref_sync()

[Jiri Pirko]

Fri, Jul 10, 2026 at 09:36:25PM +0200, ivecera@xxxxxxxxxx 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@xxxxxxxxxx>

Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>