acls+kerberos (limitation)

acls+kerberos (limitation)

[Olga Kornievskaia]

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?

Thank you.

Re: acls+kerberos (limitation)

[Trond Myklebust]

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?

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com

Re: acls+kerberos (limitation)

[Olga Kornievskaia]

On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@hammerspace.com> 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.

> --
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@hammerspace.com
>
>

Re: acls+kerberos (limitation)

[Chuck Lever]

> On Dec 18, 2019, at 2:31 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> 
> On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@hammerspace.com> 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.

--
Chuck Lever

Re: acls+kerberos (limitation)

[Olga Kornievskaia]

On Wed, Dec 18, 2019 at 2:34 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>
>
>
> > On Dec 18, 2019, at 2:31 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> >
> > On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@hammerspace.com> 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.

> --
> Chuck Lever
>
>
>

Re: acls+kerberos (limitation)

[Chuck Lever]

> On Dec 20, 2019, at 1:15 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> 
> On Wed, Dec 18, 2019 at 2:34 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>> 
>> 
>> 
>>> On Dec 18, 2019, at 2:31 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
>>> 
>>> On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@hammerspace.com> 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.


--
Chuck Lever

Re: acls+kerberos (limitation)

[Olga Kornievskaia]

On Fri, Dec 20, 2019 at 1:28 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>
>
>
> > On Dec 20, 2019, at 1:15 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> >
> > On Wed, Dec 18, 2019 at 2:34 PM Chuck Lever <chuck.lever@oracle.com> wrote:
> >>
> >>
> >>
> >>> On Dec 18, 2019, at 2:31 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> >>>
> >>> On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@hammerspace.com> 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
>
>
>

Re: acls+kerberos (limitation)

[Chuck Lever]

> On Dec 20, 2019, at 3:04 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> 
> On Fri, Dec 20, 2019 at 1:28 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>> 
>> 
>> 
>>> On Dec 20, 2019, at 1:15 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
>>> 
>>> On Wed, Dec 18, 2019 at 2:34 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>>>> 
>>>> 
>>>> 
>>>>> On Dec 18, 2019, at 2:31 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
>>>>> 
>>>>> On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@hammerspace.com> 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?

Why is using the NFSv4.1 session max reply size not possible? For
NFSv4.0, rsize seems reasonable to me.


--
Chuck Lever

Re: acls+kerberos (limitation)

[Olga Kornievskaia]

On Fri, Dec 20, 2019 at 3:11 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>
>
>
> > On Dec 20, 2019, at 3:04 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> >
> > On Fri, Dec 20, 2019 at 1:28 PM Chuck Lever <chuck.lever@oracle.com> wrote:
> >>
> >>
> >>
> >>> On Dec 20, 2019, at 1:15 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> >>>
> >>> On Wed, Dec 18, 2019 at 2:34 PM Chuck Lever <chuck.lever@oracle.com> wrote:
> >>>>
> >>>>
> >>>>
> >>>>> On Dec 18, 2019, at 2:31 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> >>>>>
> >>>>> On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@hammerspace.com> 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?
>
> Why is using the NFSv4.1 session max reply size not possible? For
> NFSv4.0, rsize seems reasonable to me.

It's not possible because there is a hard limit of number of pages the
code will allocate (right now).

static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf,
size_t buflen)
{
        struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };

NFS4ACL_MAXPAGES are based on the 64K limit (from the XATTR_MAX_SIZE).

        if (npages > ARRAY_SIZE(pages))
                return -ERANGE;

Typically session size (or r/wsizes) are something like 262K or 1M.

I was just saying that I'd then would need to remove the static
structure for pages and make it dynamic based on the (rsize or session
size). I thought that r/wsize was set to whatever the session sizes
are so using the r/wsize values would make it work for both 4.0 and
4.1+.



>
> --
> Chuck Lever
>
>
>

Re: acls+kerberos (limitation)

[Chuck Lever]

> On Dec 20, 2019, at 3:53 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> 
> On Fri, Dec 20, 2019 at 3:11 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>> 
>> 
>> 
>>> On Dec 20, 2019, at 3:04 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
>>> 
>>> On Fri, Dec 20, 2019 at 1:28 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>>>> 
>>>> 
>>>> 
>>>>> On Dec 20, 2019, at 1:15 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
>>>>> 
>>>>> On Wed, Dec 18, 2019 at 2:34 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>>> On Dec 18, 2019, at 2:31 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
>>>>>>> 
>>>>>>> On Wed, Dec 18, 2019 at 2:05 PM Trond Myklebust <trondmy@hammerspace.com> 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?
>> 
>> Why is using the NFSv4.1 session max reply size not possible? For
>> NFSv4.0, rsize seems reasonable to me.
> 
> It's not possible because there is a hard limit of number of pages the
> code will allocate (right now).
> 
> static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf,
> size_t buflen)
> {
>        struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };
> 
> NFS4ACL_MAXPAGES are based on the 64K limit (from the XATTR_MAX_SIZE).
> 
>        if (npages > ARRAY_SIZE(pages))
>                return -ERANGE;
> 
> Typically session size (or r/wsizes) are something like 262K or 1M.
> 
> I was just saying that I'd then would need to remove the static
> structure for pages and make it dynamic based on the (rsize or session
> size).

IMO you should do that. There should be a page array available in
the recv XDR buffer.


> I thought that r/wsize was set to whatever the session sizes
> are so using the r/wsize values would make it work for both 4.0 and
> 4.1+.

<shrug> OK... that choice should be documented in a comment.

--
Chuck Lever