On Fri, Dec 20, 2019 at 1:28 PM Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: > > > > > On Dec 20, 2019, at 1:15 PM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: > > > > On Wed, Dec 18, 2019 at 2:34 PM Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: > >> > >> > >> > >>> On Dec 18, 2019, at 2:31 PM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: > >>> > >>> On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > >>>> > >>>> On Wed, 2019-12-18 at 12:47 -0500, Olga Kornievskaia wrote: > >>>>> Hi folks, > >>>>> > >>>>> Is this a well know but undocumented fact that you can't set large > >>>>> amount of acls (over 4096bytes, ~90acls) while mounted using > >>>>> krb5i/krb5p? That if you want to get/set large acls, it must be done > >>>>> over auth_sys/krb5? > >>>>> > >>>> > >>>> It's certainly not something that I was aware of. Do you see where that > >>>> limitation is coming from? > >>> > >>> I haven't figure it exactly but gss_unwrap_resp_integ() is failing in > >>> if (mic_offset > rcv_buf->len). I'm just not sure who sets up the > >>> buffer (or why rvc_buf->len is (4280) larger than a page can a > >>> page-limit might make sense to for me but it's not). So you think it > >>> should have been working. > >> > >> The buffer is set up in the XDR encoder. But pages can be added > >> by the transport... I guess rcv_buf->len isn't updated when that > >> happens. > >> > > > > Here's why the acl+krbi/krb5p is failing. > > > > acl tool first calls into the kernel to find out how large of a buffer > > it needs to supply and gets acl size then calls down again then code > > in __nfs4_get_acl_uncached() allocates a number of pages (this what > > set's the available buffer length later used by the sunrpc code). That > > works for non-integrity because in call_decode() the call > > rpc_unwrap_resp() doesn't try to calculate the checksum on the buffer > > that was just read. However, when its krb5i/krb5p we have truncated > > buffer and mic offset that's larger than the existing buffer. > > > > I think something needs to be marked to skip doing gss for the initial > > acl query? I first try providing more space in > > __nfs4_get_acl_uncached() for when authflavor=krb5i/krb5p and buflen=0 > > but no matter what the number is the received acl can be larger than > > that thus I don't think that's a good approach. > > It's not strictly true that the received ACL can be always be larger. > There is an upper bound on request sizes. > > My preference has always been to allocate a receive buffer of the maximum > size before the call, just like every other request works. I can't think > of any reason why retrieving an ACL has to be different. Then we can get > rid of the hack in the transports to fill in those pages behind the back > of the upper layers. > > The issue here has always been that there's no way for the client to > discover the number of bytes it needs to retrieve before it sets up the > GETACL. > > For NFSv4.1+ you can probably assume that the ACL will never be larger > than the session's maximum reply size. > > For NFSv4.0 you'll have to make something up. > > But allocating a large receive buffer for this request is the only way to > make the receive reliable. You should be able to do that by stuffing the > recv XDR buffer with individual pages, just like nfsd does, in GETACL's > encoding function. > > Others might have a different opinion. Or I might have completely > misunderstood the issue. > Putting a limit would be easier. I thought of using rsize (wsize) as we can't get anything larger than in the payload that but that's not possible. Because the code sets limits based on XATTR_MAX_SIZE which is a linux server side limitation and it doesn't seem to be appropriate to be applied as a generic implementation. Would it be ok to change the static memory allocation to be dynamic and based on the rsize? Thoughts? > > -- > Chuck Lever > > >
