MUP.SYS and SAMBA Interoperability

[Ladislav Ardo]

gentleman,

I'd like to report a bug (very likely M$ one, but yeah...)

Last week we have discovered that clicking on "non existent" SAMBA share 
causes direct crash of XP SP2 and more recent M$ OS'es (2003 SP2, R2 etc.).

The result is same...client reboots and when it comes back it recovers 
from a "serious error".

Machine1: Error code 1000007e, parameter1 c0000005, parameter2 80881b5e, 
parameter3 f78e6b80, parameter4 f78e687c.

Machine2: Error code 1000007e, parameter1 c0000005, parameter2 804e1928, 
parameter3 b9f10c58, parameter4 b9f10954.

I have analysed minidumps from from both machines and discovered that 
Mup.Sys is causing the reboot.

MUP.SYS (MUP = Multiple UNC Provider)

http://technet2.microsoft.com/WindowsServer/en/library/7261fd0a-e5a7-4236-a89f-29f79d13d1561033.mspx?mfr=true 


To reproduce it simply create a samba share with similar settings:

[frabwinxp]
        comment = local home directories
        path = /export/home3/%S
        valid users = %S @admins
        read only = no
        browseable = yes
        msdfs root = yes
        admin users = @admins
        dos filemode = yes
        create mask = 0774
        directory mask = 0774
        inherit permissions = yes
        follow symlinks = yes
        strict allocate = yes
        msdfs root = yes

Where /export/home3/%S does not exist. Upon restarting of Samba, the 
share will appear from Windows explorer on clients 
(\\%servername\frabwinxp) but is of course inaccessible since the path 
does not exist. Clicking on the share twice from Microsoft explorer will 
(amazingly enough) cause BSOD and/ or reboot of the XP SP2 clients and 
2003 Server SP1, R2.

Solution:

On affected clients I have added the following key to the registry and 
rebooted:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Mup
DisableDFS: REG_DWORD: range: 0 or 1
Default: 1

1=Enabled, 0=Disabled thus default value "1" disables the MUP. Once you 
reboot the problem is away.

If you change it back again to 0 and reboot clicking on "non-existent" 
samba share will crash clients with aforementioned OS's.

Anyway, it may be something you know about, just thought I post it in 
case you haven't come across the problem yet.

regards,
Ladislav.