Created attachment 210065 [details]
patch

Overview:
The 'args' and 'ivars' malloc()s do not have associated free()s.  See lines 397 and 488 of https://svnweb.freebsd.org/base/head/sys/dev/mii/mii.c?annotate=326255.

Here is a proposed fix for this.  

The 'ivars' leak is simple to fix.  Just adding a free in the miibus_detach() solved the issue.

The 'args' leak is a little more complicated.  This is malloc()ed for each phy on the bus "child".  There is currently no detach function for the child.  Added miibus_child_detached() to free the 'args'. 


Steps to Reproduce:
Attach and detach a module with mii devices.  Observe leaks.
# devinfo -v | grep re0
            re0 pnpinfo vendor=0x10ec device=0x8168 subvendor=0x10ec subdevice=0x0123 class=0x020000 at slot=0 function=0 dbsf=pci0:3:0:0 handle=\_SB_.PCI0.RP02.PXSX
# 
# devctl detach pci0:3:0:0
#
# vmstat -m | grep devbuf
       devbuf 34770 70136K       -    35686  16,32,64,128,256,512,1024,2048,4096,8192,65536
# devctl attach pci0:3:0:0 
# vmstat -m | grep devbuf
       devbuf 35307 70188K       -    36223  16,32,64,128,256,512,1024,2048,4096,8192,65536
# devctl detach pci0:3:0:0
# vmstat -m | grep devbuf
       devbuf 34779 70122K       -    36223  16,32,64,128,256,512,1024,2048,4096,8192,65536
# 


Actual Results: 
're' LEAKED 9 times of type 'devbuf' (M_DEVBUF).  2 of these leaks are from the 'mii' device.


Expected Results:
Not to leak (or in the 're' case leak less).


Build Date & Hardware:
HEADr355854 on amd64 target with any hardware with mii device(s)