most: usb: Fix use-after-free in hdm_disconnect

hdm_disconnect() calls most_deregister_interface(), which eventually
unregisters the MOST interface device with device_unregister(iface->dev).
If that drops the last reference, the device core may call release_mdev()
immediately while hdm_disconnect() is still executing.

The old code also freed several mdev-owned allocations in
hdm_disconnect() and then performed additional put_device() calls.
Depending on refcount order, this could lead to use-after-free or
double-free when release_mdev() ran (or when unregister paths also
performed puts).

Fix by moving the frees of mdev-owned allocations into release_mdev(),
so they happen exactly once when the device is truly released, and by
dropping the extra put_device() calls in hdm_disconnect() that are
redundant after device_unregister() and most_deregister_interface().

This addresses the KASAN slab-use-after-free reported by syzbot in
hdm_disconnect(). See report and stack traces in the bug link below.

Reported-by:  <syzbot+916742d5d24f6c254761@syzkaller.appspotmail.com>
Cc: stable <stable@kernel.org>
Closes: https://syzkaller.appspot.com/bug?extid=916742d5d24f6c254761


Fixes: 97a6f772 ("drivers: most: add USB adapter driver")
Signed-off-by: Victoria Votokina <Victoria.Votokina@kaspersky.com>
Link: https://patch.msgid.link/20251010105241.4087114-2-Victoria.Votokina@kaspersky.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>