[cifs-protocol] SMB2 mixed lock & unlock requests in a single SMB_LOCK request

Steven Danneman steven.danneman at isilon.com
Mon Nov 30 16:57:35 MST 2009



I've come across another SMB2 locking issue that I can't find explicit
documentation for in MS-SMB2 (v18.0).


My first question, is whether a single SMB_LOCK request can contain both
unlock and lock requests as the LockingAndX command type in SMBv1 could?
The MS-SMB2 document hints that the answer to this question is "no" but
it doesn't seem to explicitly state it anywhere.


Section 2.2.26 states: "The SMB2 LOCK Request packet is sent by the
client to either lock or unlock portions of a file." 


This statement is ambiguous as to whether the "or" is inclusive or


In my testing, sending both lock and unlock requests in a single SMB2
locking request returns a STATUS_INVALID_PARAMETER.  However, if the
requests are ordered such that a unlock structure come first, the unlock
request seems to succeed.


The attached pcap, against W2K8R2 shows:


1) Packet 27-28:  A single lock request succeeding on range 0-10.

2) Packet 29-30:  A lock request with unlock(0-10) and lock(10-10)

3) Packet 31-32:  A lock request with lock(0-10) and lock(10-10)
succeeding, showing that the previous request, though it returned an
error, succeeded in unlocking.


It seems to me the server behavior should be to return
STATUS_INVALID_PARAMETER without completing any of the lock/unlock
requests when they are mixed.  Both the fact that this isn't allowed,
and the W2K8R2 behavior deviation should be documented.



Steven Danneman | Software Development Engineer
Isilon Systems    P +1-206-315-7500     F  +1-206-315-7501

    How breakthroughs begin. (tm)


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