CVE-2022-50545

In the Linux kernel, the following vulnerability has been resolved:

r6040: Fix kmemleak in probe and remove

There is a memory leaks reported by kmemleak:

unreferenced object 0xffff888116111000 (size 2048): comm "modprobe", pid 817, jiffies 4294759745 (age 76.502s) hex dump (first 32 bytes): 00 c4 0a 04 81 88 ff ff 08 10 11 16 81 88 ff ff ................ 08 10 11 16 81 88 ff ff 00 00 00 00 00 00 00 00 ................ backtrace: [<ffffffff815bcd82>] kmalloctrace+0x22/0x60 [<ffffffff827e20ee>] phydevicecreate+0x4e/0x90 [<ffffffff827e6072>] getphydevice+0xd2/0x220 [<ffffffff827e7844>] mdiobusscan+0xa4/0x2e0 [<ffffffff827e8be2>] _mdiobusregister+0x482/0x8b0 [<ffffffffa01f5d24>] r6040initone+0x714/0xd2c [r6040] ...

The problem occurs in probe process as follows: r6040initone: mdiobusregister mdiobusscan <- alloc and register phydevice, the reference count of phydevice is 3 r6040miiprobe phyconnect <- connect to the first phydevice, so the reference count of the first phydevice is 4, others are 3 registernetdev <- fault inject succeeded, goto error handling path

// error handling path
err_out_mdio_unregister:
  mdiobus_unregister(lp->mii_bus);
err_out_mdio:
  mdiobus_free(lp->mii_bus);    <- the reference count of the first
                                   phy_device is 1, it is not released
                                   and other phy_devices are released

// similarly, the remove process also has the same problem

The root cause is traced to the phydevice is not disconnected when removes one r6040 device in r6040removeone() or on error handling path after r6040mii probed successfully. In r6040miiprobe(), a net ethernet device is connected to the first PHY device of miibus, in order to notify the connected driver when the link status changes, which is the default behavior of the PHY infrastructure to handle everything. Therefore the phydevice should be disconnected when removes one r6040 device or on error handling path.

Fix it by adding phydisconnect() when removes one r6040 device or on error handling path after r6040mii probed successfully.