phy: lynx-28g: reject probing on devices with unsupported OF nodes

phy: lynx-28g: reject probing on devices with unsupported OF nodes

It is possible to bind the lynx-28g driver to an arbitrary device with
an OF node, using the driver_override mechanism that is available for
the platform bus, and trigger a crash this way:

$ echo 1ea0000.serdes > /sys/bus/platform/drivers/lynx-10g/unbind
$ echo lynx-28g > /sys/bus/platform/devices/1ea0000.serdes/driver_override
$ echo 1ea0000.serdes > /sys/bus/platform/drivers/lynx-28g/bind
Internal error: Oops: 0000000096000004 [#1]  SMP
Hardware name: LS1028A RDB Board (DT)
pc : lynx_probe+0x118/0x4fc
lr : lynx_probe+0x110/0x4fc
Call trace:
 lynx_probe+0x118/0x4fc (P)
 lynx_28g_probe+0x54/0x7c
 platform_probe+0x68/0xa4
 really_probe+0x14c/0x2ec
 __driver_probe_device+0xc8/0x170
 device_driver_attach+0x58/0xa8
 bind_store+0xd8/0x118
 drv_attr_store+0x24/0x38

The crash is caused by the fact that of_device_get_match_data() returns
NULL (the bound device has a different compatible string) and this is
not checked.

There was a previous attempt to avoid this in commit c9d80e861034 ("phy:
lynx-28g: require an OF node to probe"), but the mechanism was not fully
understood and it only covered the case where the driver was bound to a
device with no OF node.

The issue was found during Sashiko review. Elevated privilege is
required to override the driver for a device, so the real life impact of
the issue should not be very high.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20260610151952.2141019-3-vladimir.oltean@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>