Hi Olga- > On May 25, 2018, at 7:02 AM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: > > Thank you for the comments. Will hopefully address them in the next version. > > On Thu, May 24, 2018 at 8:50 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: >> Hi Olga- >> >>> On May 24, 2018, at 1:05 PM, Olga Kornievskaia <kolga@xxxxxxxxxx> wrote: >>> >>> If the user supplies a clientaddr value, >> >> Please say "NFS client administrator" not "user". A >> "user" is any non-privileged user, so saying that a >> "user" can set this value is misleading. > > Ok will change it. > >>> it should be either >>> a special value of either IPV4/IPV6 any address or a local address >>> on the same network that the server being mounted. >> >> This option should allow any local address the client has, >> not just an address that is on the same network as the >> server. See below for further explanation. > > Ok, I added this to the comment specifically as I didn't know if this > would pose a problem. I didn't know if allowing any address was useful > as when it's not specified the address on the same network as the > server is chosen. Yep, any of the client's local addresses should be allowed. >>> Otherwise, we >>> disallow the client to use an arbitrary value of the clientaddr value. >>> This value is used to construct a client id of SETCLIENTID and >>> providing a false value can interfere with the real owner's mount. >> >> The patch description is misleading: >> >> Interference occurs only if the real owner's lease is >> not protected by Kerberos AND this client has the same >> client ID string as another client. > > Ok I will add this more explicit detail when the interference occurs > (when neither of the machines are using Kerberos and the other client > machine is not using a module parameter to add a unique identifier to > the client ID string). I think otherwise it is knowns that client ID > is created with the value of the clientaddr. The only way a problem occurs is if the clientaddr is the same AND the cl_nodename is the same. How is that happening? Why are the cl_nodenames the same? If they are not the same, then it is not possible that the clients' leases are inter- fering with each other, and something else is going on. >> The Linux client's client ID string also contains the >> system's cl_nodename. Both the cl_nodename and the >> callback address have to be the same as some other >> client's, and they both have to be Linux, for this to >> be a problem. >> >> It's more likely that the customer's clients are all >> named the same (maybe they are copied from the same >> system image), and reverse DNS lookup is giving them >> all the same clientaddr= . That's an unsupported >> configuration and there are already ways to address >> this. >> >> Or perhaps I don't understand the use case that is >> causing the problem. Can the patch description explain >> why your customer is trying to set clientaddr= ? > > The customer case was a simple mistake of including the wrong address. But that doesn't answer the question. Why did the customer feel the need to set clientaddr= ? > Do you fundamentally disagree that there is a case for > denial-of-service here? The only service that is affected if the clientaddr is set incorrectly is on the client where the mistake occurs. If the cl_nodenames are all unique then other clients should not be affected by the mistake. If that is happening, that's a server bug. If the problem was that the customer set the wrong address, let's say that, rather than claiming that the patch prevents lease tampering. -- Chuck Lever -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
