[PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Weston Andros Adamson]

Fix a bug where getxattr returns ERANGE when the attr buffer
length is close enough to the nearest PAGE_SIZE multiple that adding
the extra bytes leaves too little room for the ACL buffer.

Besides storing the ACL buffer, the getacl decoder uses the inline
pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
must allocate enough page space for all of the data to be decoded.

This patch uses xdr_partial_copy_from_skb to allocate any needed
pages past the first one. This allows the client to always cache the acl
on the first getacl call and not just if it fits in one page.

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
---

Version 2 of this patch changes things up a bit:

 - rely on xdr_partial_copy_from_skb to allocate pages as needed
 - always allocate 1 page as there will be some data
 - allow xdr_partial_copy_from_skb to allocate up to NFS4ACL_MAXPAGES + 1 pages
   to hold the max size ACL and the extra page for the bitmap and acl length
 - this allows the first request for an ACL to be cached - not just when it
   fits in one page

 fs/nfs/nfs4proc.c | 40 +++++++++++++++-------------------------
 fs/nfs/nfs4xdr.c  |  2 --
 2 files changed, 15 insertions(+), 27 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index ca36d0d..dc8e4f5 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4430,20 +4430,17 @@ out:
 /*
  * The getxattr API returns the required buffer length when called with a
  * NULL buf. The NFSv4 acl tool then calls getxattr again after allocating
- * the required buf.  On a NULL buf, we send a page of data to the server
- * guessing that the ACL request can be serviced by a page. If so, we cache
- * up to the page of ACL data, and the 2nd call to getxattr is serviced by
- * the cache. If not so, we throw away the page, and cache the required
- * length. The next getxattr call will then produce another round trip to
- * the server, this time with the input buf of the required size.
+ * the required buf. Cache the result from the first getxattr call to avoid
+ * sending another RPC.
  */
 static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t buflen)
 {
-	struct page *pages[NFS4ACL_MAXPAGES] = {NULL, };
+	/* enough pages to hold ACL data plus the bitmap and acl length */
+	struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };
 	struct nfs_getaclargs args = {
 		.fh = NFS_FH(inode),
+		/* The xdr layer may allocate pages here. */
 		.acl_pages = pages,
-		.acl_len = buflen,
 	};
 	struct nfs_getaclres res = {
 		.acl_len = buflen,
@@ -4453,32 +4450,25 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
 		.rpc_argp = &args,
 		.rpc_resp = &res,
 	};
-	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
 	int ret = -ENOMEM, i;
 
-	/* As long as we're doing a round trip to the server anyway,
-	 * let's be prepared for a page of acl data. */
-	if (npages == 0)
-		npages = 1;
-	if (npages > ARRAY_SIZE(pages))
-		return -ERANGE;
-
-	for (i = 0; i < npages; i++) {
-		pages[i] = alloc_page(GFP_KERNEL);
-		if (!pages[i])
-			goto out_free;
-	}
+	/*
+	 * There will be some data returned by the server, how much is not
+	 * known yet. Allocate one page and let the XDR layer allocate
+	 * more if needed.
+	 */
+	pages[0] = alloc_page(GFP_KERNEL);
 
 	/* for decoding across pages */
 	res.acl_scratch = alloc_page(GFP_KERNEL);
 	if (!res.acl_scratch)
 		goto out_free;
 
-	args.acl_len = npages * PAGE_SIZE;
+	args.acl_len = ARRAY_SIZE(pages) << PAGE_SHIFT;
 	args.acl_pgbase = 0;
 
-	dprintk("%s  buf %p buflen %zu npages %d args.acl_len %zu\n",
-		__func__, buf, buflen, npages, args.acl_len);
+	dprintk("%s  buf %p buflen %zu args.acl_len %zu\n",
+		__func__, buf, buflen, args.acl_len);
 	ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode),
 			     &msg, &args.seq_args, &res.seq_res, 0);
 	if (ret)
@@ -4503,7 +4493,7 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
 out_ok:
 	ret = res.acl_len;
 out_free:
-	for (i = 0; i < npages; i++)
+	for (i = 0; i < ARRAY_SIZE(pages) && pages[i]; i++)
 		if (pages[i])
 			__free_page(pages[i]);
 	if (res.acl_scratch)
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 5be2868..4e2e2da 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -5207,8 +5207,6 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
 	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
 		goto out;
 
-	xdr_enter_page(xdr, xdr->buf->page_len);
-
 	/* Calculate the offset of the page data */
 	pg_offset = xdr->buf->head[0].iov_len;
 
-- 
1.8.3.1 (Apple Git-46)

Re: [PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Trond Myklebust]

On Thu, 2013-11-21 at 16:20 -0500, Weston Andros Adamson wrote:
> Fix a bug where getxattr returns ERANGE when the attr buffer
> length is close enough to the nearest PAGE_SIZE multiple that adding
> the extra bytes leaves too little room for the ACL buffer.
> 
> Besides storing the ACL buffer, the getacl decoder uses the inline
> pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
> must allocate enough page space for all of the data to be decoded.
> 
> This patch uses xdr_partial_copy_from_skb to allocate any needed
> pages past the first one. This allows the client to always cache the acl
> on the first getacl call and not just if it fits in one page.
> 
> Signed-off-by: Weston Andros Adamson <dros@netapp.com>
> ---
> 
> Version 2 of this patch changes things up a bit:
> 
>  - rely on xdr_partial_copy_from_skb to allocate pages as needed
>  - always allocate 1 page as there will be some data
>  - allow xdr_partial_copy_from_skb to allocate up to NFS4ACL_MAXPAGES + 1 pages
>    to hold the max size ACL and the extra page for the bitmap and acl length
>  - this allows the first request for an ACL to be cached - not just when it
>    fits in one page
> 
>  fs/nfs/nfs4proc.c | 40 +++++++++++++++-------------------------
>  fs/nfs/nfs4xdr.c  |  2 --
>  2 files changed, 15 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index ca36d0d..dc8e4f5 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -4430,20 +4430,17 @@ out:
>  /*
>   * The getxattr API returns the required buffer length when called with a
>   * NULL buf. The NFSv4 acl tool then calls getxattr again after allocating
> - * the required buf.  On a NULL buf, we send a page of data to the server
> - * guessing that the ACL request can be serviced by a page. If so, we cache
> - * up to the page of ACL data, and the 2nd call to getxattr is serviced by
> - * the cache. If not so, we throw away the page, and cache the required
> - * length. The next getxattr call will then produce another round trip to
> - * the server, this time with the input buf of the required size.
> + * the required buf. Cache the result from the first getxattr call to avoid
> + * sending another RPC.
>   */
>  static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t buflen)
>  {
> -	struct page *pages[NFS4ACL_MAXPAGES] = {NULL, };
> +	/* enough pages to hold ACL data plus the bitmap and acl length */
> +	struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };

Why the change to the array length? From what I can see, you are making
everything else depend on ARRAY_LENGTH(pages).

>  	struct nfs_getaclargs args = {
>  		.fh = NFS_FH(inode),
> +		/* The xdr layer may allocate pages here. */
>  		.acl_pages = pages,
> -		.acl_len = buflen,
>  	};
>  	struct nfs_getaclres res = {
>  		.acl_len = buflen,
> @@ -4453,32 +4450,25 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
>  		.rpc_argp = &args,
>  		.rpc_resp = &res,
>  	};
> -	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
>  	int ret = -ENOMEM, i;
>  
> -	/* As long as we're doing a round trip to the server anyway,
> -	 * let's be prepared for a page of acl data. */
> -	if (npages == 0)
> -		npages = 1;
> -	if (npages > ARRAY_SIZE(pages))
> -		return -ERANGE;
> -
> -	for (i = 0; i < npages; i++) {
> -		pages[i] = alloc_page(GFP_KERNEL);
> -		if (!pages[i])
> -			goto out_free;
> -	}
> +	/*
> +	 * There will be some data returned by the server, how much is not
> +	 * known yet. Allocate one page and let the XDR layer allocate
> +	 * more if needed.
> +	 */
> +	pages[0] = alloc_page(GFP_KERNEL);
>  
>  	/* for decoding across pages */
>  	res.acl_scratch = alloc_page(GFP_KERNEL);
>  	if (!res.acl_scratch)
>  		goto out_free;
>  
> -	args.acl_len = npages * PAGE_SIZE;
> +	args.acl_len = ARRAY_SIZE(pages) << PAGE_SHIFT;
>  	args.acl_pgbase = 0;
>  
> -	dprintk("%s  buf %p buflen %zu npages %d args.acl_len %zu\n",
> -		__func__, buf, buflen, npages, args.acl_len);
> +	dprintk("%s  buf %p buflen %zu args.acl_len %zu\n",
> +		__func__, buf, buflen, args.acl_len);
>  	ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode),
>  			     &msg, &args.seq_args, &res.seq_res, 0);
>  	if (ret)
> @@ -4503,7 +4493,7 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
>  out_ok:
>  	ret = res.acl_len;
>  out_free:
> -	for (i = 0; i < npages; i++)
> +	for (i = 0; i < ARRAY_SIZE(pages) && pages[i]; i++)
>  		if (pages[i])
>  			__free_page(pages[i]);

What happens now when the server tries to return an ACL that won't fit
in the above array? Do we still return ERANGE?

Also, are we still safe w.r.t. checking that we don't copy more than
'buflen' bytes of data?

>  	if (res.acl_scratch)
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index 5be2868..4e2e2da 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -5207,8 +5207,6 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>  	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
>  		goto out;
>  
> -	xdr_enter_page(xdr, xdr->buf->page_len);

Why is this being removed?

> -
>  	/* Calculate the offset of the page data */
>  	pg_offset = xdr->buf->head[0].iov_len;
>  

Re: [PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Weston Andros Adamson]

On Dec 10, 2013, at 1:13 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote:

> On Thu, 2013-11-21 at 16:20 -0500, Weston Andros Adamson wrote:
>> Fix a bug where getxattr returns ERANGE when the attr buffer
>> length is close enough to the nearest PAGE_SIZE multiple that adding
>> the extra bytes leaves too little room for the ACL buffer.
>> 
>> Besides storing the ACL buffer, the getacl decoder uses the inline
>> pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
>> must allocate enough page space for all of the data to be decoded.
>> 
>> This patch uses xdr_partial_copy_from_skb to allocate any needed
>> pages past the first one. This allows the client to always cache the acl
>> on the first getacl call and not just if it fits in one page.
>> 
>> Signed-off-by: Weston Andros Adamson <dros@netapp.com>
>> ---
>> 
>> Version 2 of this patch changes things up a bit:
>> 
>> - rely on xdr_partial_copy_from_skb to allocate pages as needed
>> - always allocate 1 page as there will be some data
>> - allow xdr_partial_copy_from_skb to allocate up to NFS4ACL_MAXPAGES + 1 pages
>>   to hold the max size ACL and the extra page for the bitmap and acl length
>> - this allows the first request for an ACL to be cached - not just when it
>>   fits in one page
>> 
>> fs/nfs/nfs4proc.c | 40 +++++++++++++++-------------------------
>> fs/nfs/nfs4xdr.c  |  2 --
>> 2 files changed, 15 insertions(+), 27 deletions(-)
>> 
>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>> index ca36d0d..dc8e4f5 100644
>> --- a/fs/nfs/nfs4proc.c
>> +++ b/fs/nfs/nfs4proc.c
>> @@ -4430,20 +4430,17 @@ out:
>> /*
>>  * The getxattr API returns the required buffer length when called with a
>>  * NULL buf. The NFSv4 acl tool then calls getxattr again after allocating
>> - * the required buf.  On a NULL buf, we send a page of data to the server
>> - * guessing that the ACL request can be serviced by a page. If so, we cache
>> - * up to the page of ACL data, and the 2nd call to getxattr is serviced by
>> - * the cache. If not so, we throw away the page, and cache the required
>> - * length. The next getxattr call will then produce another round trip to
>> - * the server, this time with the input buf of the required size.
>> + * the required buf. Cache the result from the first getxattr call to avoid
>> + * sending another RPC.
>>  */
>> static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t buflen)
>> {
>> -	struct page *pages[NFS4ACL_MAXPAGES] = {NULL, };
>> +	/* enough pages to hold ACL data plus the bitmap and acl length */
>> +	struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };
> 
> Why the change to the array length? From what I can see, you are making
> everything else depend on ARRAY_LENGTH(pages).

So we can fit NFS4ACL_MAXPAGES (which is XATTR_SIZE_MAX / PAGE_SIZE) AND the bitmap (which being variable length must also use the inline pages), otherwise we will always fail for ACL data sized near XATTR_SIZE_MAX, even though we should support it.  I figure that a page is more than enough for the bitmap even when future-proofing nfsv4.X, but we’ll always need that extra page when the actual ACL data is XATTR_SIZE bytes long. 

> 
>> 	struct nfs_getaclargs args = {
>> 		.fh = NFS_FH(inode),
>> +		/* The xdr layer may allocate pages here. */
>> 		.acl_pages = pages,
>> -		.acl_len = buflen,
>> 	};
>> 	struct nfs_getaclres res = {
>> 		.acl_len = buflen,
>> @@ -4453,32 +4450,25 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
>> 		.rpc_argp = &args,
>> 		.rpc_resp = &res,
>> 	};
>> -	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
>> 	int ret = -ENOMEM, i;
>> 
>> -	/* As long as we're doing a round trip to the server anyway,
>> -	 * let's be prepared for a page of acl data. */
>> -	if (npages == 0)
>> -		npages = 1;
>> -	if (npages > ARRAY_SIZE(pages))
>> -		return -ERANGE;
>> -
>> -	for (i = 0; i < npages; i++) {
>> -		pages[i] = alloc_page(GFP_KERNEL);
>> -		if (!pages[i])
>> -			goto out_free;
>> -	}
>> +	/*
>> +	 * There will be some data returned by the server, how much is not
>> +	 * known yet. Allocate one page and let the XDR layer allocate
>> +	 * more if needed.
>> +	 */
>> +	pages[0] = alloc_page(GFP_KERNEL);
>> 
>> 	/* for decoding across pages */
>> 	res.acl_scratch = alloc_page(GFP_KERNEL);
>> 	if (!res.acl_scratch)
>> 		goto out_free;
>> 
>> -	args.acl_len = npages * PAGE_SIZE;
>> +	args.acl_len = ARRAY_SIZE(pages) << PAGE_SHIFT;
>> 	args.acl_pgbase = 0;
>> 
>> -	dprintk("%s  buf %p buflen %zu npages %d args.acl_len %zu\n",
>> -		__func__, buf, buflen, npages, args.acl_len);
>> +	dprintk("%s  buf %p buflen %zu args.acl_len %zu\n",
>> +		__func__, buf, buflen, args.acl_len);
>> 	ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode),
>> 			     &msg, &args.seq_args, &res.seq_res, 0);
>> 	if (ret)
>> @@ -4503,7 +4493,7 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
>> out_ok:
>> 	ret = res.acl_len;
>> out_free:
>> -	for (i = 0; i < npages; i++)
>> +	for (i = 0; i < ARRAY_SIZE(pages) && pages[i]; i++)
>> 		if (pages[i])
>> 			__free_page(pages[i]);
> 
> What happens now when the server tries to return an ACL that won't fit
> in the above array? Do we still return ERANGE?

Yes, the XDR layer will set NFS4_ACL_TRUNC if the ACL data doesn’t fit in args.acl_len, and __nfs4_get_acl_uncached still checks for this flag, returning -ERANGE if set.

> 
> Also, are we still safe w.r.t. checking that we don't copy more than
> 'buflen' bytes of data?

Yes, the xdr inline page filler enforces this - and we set the max in nfs4_xdr_enc_getacl:

      xdr_inline_pages(&req->rq_rcv_buf, replen << 2,
                args->acl_pages, args->acl_pgbase, args->acl_len);

> 
>> 	if (res.acl_scratch)
>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>> index 5be2868..4e2e2da 100644
>> --- a/fs/nfs/nfs4xdr.c
>> +++ b/fs/nfs/nfs4xdr.c
>> @@ -5207,8 +5207,6 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>> 	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
>> 		goto out;
>> 
>> -	xdr_enter_page(xdr, xdr->buf->page_len);
> 
> Why is this being removed?

Because it BUG()s! ;)

I must admit that I don’t get why xdr_enter_page() doesn’t work when the XDR layer does the page allocation, but it does not — and the nfs3xdr ACL code (which uses the XDR layer allocation) also doesn’t call this.  It worked well without this, so I just removed it and didn’t investigate why.

-dros

> 
>> -
>> 	/* Calculate the offset of the page data */
>> 	pg_offset = xdr->buf->head[0].iov_len;
>> 
> 
> 
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Re: [PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Trond Myklebust]

On Dec 10, 2013, at 21:11, Weston Andros Adamson <dros@netapp.com> wrote:

> 
> On Dec 10, 2013, at 1:13 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote:
> 
>> On Thu, 2013-11-21 at 16:20 -0500, Weston Andros Adamson wrote:
> 
>> 
>>> 	if (res.acl_scratch)
>>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>>> index 5be2868..4e2e2da 100644
>>> --- a/fs/nfs/nfs4xdr.c
>>> +++ b/fs/nfs/nfs4xdr.c
>>> @@ -5207,8 +5207,6 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>>> 	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
>>> 		goto out;
>>> 
>>> -	xdr_enter_page(xdr, xdr->buf->page_len);
>> 
>> Why is this being removed?
> 
> Because it BUG()s! ;)
> 
> I must admit that I don’t get why xdr_enter_page() doesn’t work when the XDR layer does the page allocation, but it does not — and the nfs3xdr ACL code (which uses the XDR layer allocation) also doesn’t call this.  It worked well without this, so I just removed it and didn’t investigate why.

I’m guessing that xdr->buf>page_len is being set incorrectly by the code that does the page allocation and/or that it is failing to update xdr->buf->len and/or xdr->buf->buflen.

We really do need the xdr_enter_page() here, or the acl bitmap + data won’t be aligned properly on the page boundary.

Cheers
  Trond

Re: [PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Weston Andros Adamson]

On Dec 10, 2013, at 2:19 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote:

> 
> On Dec 10, 2013, at 21:11, Weston Andros Adamson <dros@netapp.com> wrote:
> 
>> 
>> On Dec 10, 2013, at 1:13 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote:
>> 
>>> On Thu, 2013-11-21 at 16:20 -0500, Weston Andros Adamson wrote:
>> 
>>> 
>>>> 	if (res.acl_scratch)
>>>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>>>> index 5be2868..4e2e2da 100644
>>>> --- a/fs/nfs/nfs4xdr.c
>>>> +++ b/fs/nfs/nfs4xdr.c
>>>> @@ -5207,8 +5207,6 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>>>> 	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
>>>> 		goto out;
>>>> 
>>>> -	xdr_enter_page(xdr, xdr->buf->page_len);
>>> 
>>> Why is this being removed?
>> 
>> Because it BUG()s! ;)
>> 
>> I must admit that I don’t get why xdr_enter_page() doesn’t work when the XDR layer does the page allocation, but it does not — and the nfs3xdr ACL code (which uses the XDR layer allocation) also doesn’t call this.  It worked well without this, so I just removed it and didn’t investigate why.
> 
> I’m guessing that xdr->buf>page_len is being set incorrectly by the code that does the page allocation and/or that it is failing to update xdr->buf->len and/or xdr->buf->buflen.
> 
> We really do need the xdr_enter_page() here, or the acl bitmap + data won’t be aligned properly on the page boundary.

Ok, I’ll add that back and then fix the oops… and investigate if the v3 ACL code needs it too…

Thanks,
-dros

Re: [PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Weston Andros Adamson]

Indeed, buf->page_len is still set to the maximum number of bytes in the pages array (set by xdr_inline_pages to tell xdr layer the max allocation size), and not the number of bytes that are actually present.

Working on a fix.

-dros

On Dec 10, 2013, at 3:10 PM, Weston Andros Adamson <dros@netapp.com> wrote:

> 
> On Dec 10, 2013, at 2:19 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote:
> 
>> 
>> On Dec 10, 2013, at 21:11, Weston Andros Adamson <dros@netapp.com> wrote:
>> 
>>> 
>>> On Dec 10, 2013, at 1:13 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote:
>>> 
>>>> On Thu, 2013-11-21 at 16:20 -0500, Weston Andros Adamson wrote:
>>> 
>>>> 
>>>>> 	if (res.acl_scratch)
>>>>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>>>>> index 5be2868..4e2e2da 100644
>>>>> --- a/fs/nfs/nfs4xdr.c
>>>>> +++ b/fs/nfs/nfs4xdr.c
>>>>> @@ -5207,8 +5207,6 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>>>>> 	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
>>>>> 		goto out;
>>>>> 
>>>>> -	xdr_enter_page(xdr, xdr->buf->page_len);
>>>> 
>>>> Why is this being removed?
>>> 
>>> Because it BUG()s! ;)
>>> 
>>> I must admit that I don’t get why xdr_enter_page() doesn’t work when the XDR layer does the page allocation, but it does not — and the nfs3xdr ACL code (which uses the XDR layer allocation) also doesn’t call this.  It worked well without this, so I just removed it and didn’t investigate why.
>> 
>> I’m guessing that xdr->buf>page_len is being set incorrectly by the code that does the page allocation and/or that it is failing to update xdr->buf->len and/or xdr->buf->buflen.
>> 
>> We really do need the xdr_enter_page() here, or the acl bitmap + data won’t be aligned properly on the page boundary.
> 
> Ok, I’ll add that back and then fix the oops… and investigate if the v3 ACL code needs it too…
> 
> Thanks,
> -dros
> 
> 
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Re: [PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[J. Bruce Fields]

On Thu, Nov 21, 2013 at 04:20:13PM -0500, Weston Andros Adamson wrote:
> Fix a bug where getxattr returns ERANGE when the attr buffer
> length is close enough to the nearest PAGE_SIZE multiple that adding
> the extra bytes leaves too little room for the ACL buffer.
> 
> Besides storing the ACL buffer, the getacl decoder uses the inline
> pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
> must allocate enough page space for all of the data to be decoded.
> 
> This patch uses xdr_partial_copy_from_skb to allocate any needed
> pages past the first one. This allows the client to always cache the acl
> on the first getacl call and not just if it fits in one page.

Was there some objection to this patch, or did it just get lost in the
shuffle?

Looks like it's still a bug upstream.  And it's easier to reproduce now
that we've got a) numeric id's and b) a server that can handle larger
ACLs.  I'm reliably reproducing with:

	mount -onoac f21-1:/exports/xfs2 /mnt/
	echo "A::OWNER@:RW" >ACL
	for ((i=9802; i < 10002; i++)); do echo "A::$i:RW" >>ACL; done
	echo "A::GROUP@:RW" >>ACL
	echo "A::EVERYONE@:RW" >>ACL
	nfs4_setfacl -S ACL /mnt/TEST
	strace -e getxattr nfs4_getfacl /mnt/TEST >/dev/null

which gets me

	getxattr("/mnt/TEST", "system.nfs4_acl", 0x0, 0) = 4088
	getxattr("/mnt/TEST", "system.nfs4_acl", 0x564186d89010, 4088) = -1 ERANGE (Numerical result out of range)

--b.

> 
> Signed-off-by: Weston Andros Adamson <dros@netapp.com>
> ---
> 
> Version 2 of this patch changes things up a bit:
> 
>  - rely on xdr_partial_copy_from_skb to allocate pages as needed
>  - always allocate 1 page as there will be some data
>  - allow xdr_partial_copy_from_skb to allocate up to NFS4ACL_MAXPAGES + 1 pages
>    to hold the max size ACL and the extra page for the bitmap and acl length
>  - this allows the first request for an ACL to be cached - not just when it
>    fits in one page
> 
>  fs/nfs/nfs4proc.c | 40 +++++++++++++++-------------------------
>  fs/nfs/nfs4xdr.c  |  2 --
>  2 files changed, 15 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index ca36d0d..dc8e4f5 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -4430,20 +4430,17 @@ out:
>  /*
>   * The getxattr API returns the required buffer length when called with a
>   * NULL buf. The NFSv4 acl tool then calls getxattr again after allocating
> - * the required buf.  On a NULL buf, we send a page of data to the server
> - * guessing that the ACL request can be serviced by a page. If so, we cache
> - * up to the page of ACL data, and the 2nd call to getxattr is serviced by
> - * the cache. If not so, we throw away the page, and cache the required
> - * length. The next getxattr call will then produce another round trip to
> - * the server, this time with the input buf of the required size.
> + * the required buf. Cache the result from the first getxattr call to avoid
> + * sending another RPC.
>   */
>  static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t buflen)
>  {
> -	struct page *pages[NFS4ACL_MAXPAGES] = {NULL, };
> +	/* enough pages to hold ACL data plus the bitmap and acl length */
> +	struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };
>  	struct nfs_getaclargs args = {
>  		.fh = NFS_FH(inode),
> +		/* The xdr layer may allocate pages here. */
>  		.acl_pages = pages,
> -		.acl_len = buflen,
>  	};
>  	struct nfs_getaclres res = {
>  		.acl_len = buflen,
> @@ -4453,32 +4450,25 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
>  		.rpc_argp = &args,
>  		.rpc_resp = &res,
>  	};
> -	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
>  	int ret = -ENOMEM, i;
>  
> -	/* As long as we're doing a round trip to the server anyway,
> -	 * let's be prepared for a page of acl data. */
> -	if (npages == 0)
> -		npages = 1;
> -	if (npages > ARRAY_SIZE(pages))
> -		return -ERANGE;
> -
> -	for (i = 0; i < npages; i++) {
> -		pages[i] = alloc_page(GFP_KERNEL);
> -		if (!pages[i])
> -			goto out_free;
> -	}
> +	/*
> +	 * There will be some data returned by the server, how much is not
> +	 * known yet. Allocate one page and let the XDR layer allocate
> +	 * more if needed.
> +	 */
> +	pages[0] = alloc_page(GFP_KERNEL);
>  
>  	/* for decoding across pages */
>  	res.acl_scratch = alloc_page(GFP_KERNEL);
>  	if (!res.acl_scratch)
>  		goto out_free;
>  
> -	args.acl_len = npages * PAGE_SIZE;
> +	args.acl_len = ARRAY_SIZE(pages) << PAGE_SHIFT;
>  	args.acl_pgbase = 0;
>  
> -	dprintk("%s  buf %p buflen %zu npages %d args.acl_len %zu\n",
> -		__func__, buf, buflen, npages, args.acl_len);
> +	dprintk("%s  buf %p buflen %zu args.acl_len %zu\n",
> +		__func__, buf, buflen, args.acl_len);
>  	ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode),
>  			     &msg, &args.seq_args, &res.seq_res, 0);
>  	if (ret)
> @@ -4503,7 +4493,7 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
>  out_ok:
>  	ret = res.acl_len;
>  out_free:
> -	for (i = 0; i < npages; i++)
> +	for (i = 0; i < ARRAY_SIZE(pages) && pages[i]; i++)
>  		if (pages[i])
>  			__free_page(pages[i]);
>  	if (res.acl_scratch)
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index 5be2868..4e2e2da 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -5207,8 +5207,6 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>  	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
>  		goto out;
>  
> -	xdr_enter_page(xdr, xdr->buf->page_len);
> -
>  	/* Calculate the offset of the page data */
>  	pg_offset = xdr->buf->head[0].iov_len;
>  
> -- 
> 1.8.3.1 (Apple Git-46)
> 
> --
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[PATCH] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[J. Bruce Fields]

From: Weston Andros Adamson <dros@netapp.com>

Fix a bug where getxattr returns ERANGE when the attr buffer
length is close enough to the nearest PAGE_SIZE multiple that adding
the extra bytes leaves too little room for the ACL buffer.

Besides storing the ACL buffer, the getacl decoder uses the inline
pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
must allocate enough page space for all of the data to be decoded.

This patch uses xdr_partial_copy_from_skb to allocate any needed
pages past the first one. This allows the client to always cache the acl
on the first getacl call and not just if it fits in one page.

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfs/nfs4proc.c | 40 +++++++++++++++-------------------------
 fs/nfs/nfs4xdr.c  |  2 --
 2 files changed, 15 insertions(+), 27 deletions(-)

On Mon, Dec 14, 2015 at 05:18:16PM -0500, bfields wrote:
> Looks like it's still a bug upstream.  And it's easier to reproduce now
> that we've got a) numeric id's and b) a server that can handle larger
> ACLs.  I'm reliably reproducing with:

And the same patch still applies after minor conflict resolution;
updated patch below.  I've confirmed that it eliminates the ERANGE.

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 765a03559363..2e679c295185 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4702,20 +4702,17 @@ out:
 /*
  * The getxattr API returns the required buffer length when called with a
  * NULL buf. The NFSv4 acl tool then calls getxattr again after allocating
- * the required buf.  On a NULL buf, we send a page of data to the server
- * guessing that the ACL request can be serviced by a page. If so, we cache
- * up to the page of ACL data, and the 2nd call to getxattr is serviced by
- * the cache. If not so, we throw away the page, and cache the required
- * length. The next getxattr call will then produce another round trip to
- * the server, this time with the input buf of the required size.
+ * the required buf. Cache the result from the first getxattr call to avoid
+ * sending another RPC.
  */
 static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t buflen)
 {
-	struct page *pages[NFS4ACL_MAXPAGES] = {NULL, };
+	/* enough pages to hold ACL data plus the bitmap and acl length */
+	struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };
 	struct nfs_getaclargs args = {
 		.fh = NFS_FH(inode),
+		/* The xdr layer may allocate pages here. */
 		.acl_pages = pages,
-		.acl_len = buflen,
 	};
 	struct nfs_getaclres res = {
 		.acl_len = buflen,
@@ -4725,31 +4722,24 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
 		.rpc_argp = &args,
 		.rpc_resp = &res,
 	};
-	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
 	int ret = -ENOMEM, i;
 
-	/* As long as we're doing a round trip to the server anyway,
-	 * let's be prepared for a page of acl data. */
-	if (npages == 0)
-		npages = 1;
-	if (npages > ARRAY_SIZE(pages))
-		return -ERANGE;
-
-	for (i = 0; i < npages; i++) {
-		pages[i] = alloc_page(GFP_KERNEL);
-		if (!pages[i])
-			goto out_free;
-	}
+	/*
+	 * There will be some data returned by the server, how much is not
+	 * known yet. Allocate one page and let the XDR layer allocate
+	 * more if needed.
+	 */
+	pages[0] = alloc_page(GFP_KERNEL);
 
 	/* for decoding across pages */
 	res.acl_scratch = alloc_page(GFP_KERNEL);
 	if (!res.acl_scratch)
 		goto out_free;
 
-	args.acl_len = npages * PAGE_SIZE;
+	args.acl_len = ARRAY_SIZE(pages) << PAGE_SHIFT;
 
-	dprintk("%s  buf %p buflen %zu npages %d args.acl_len %zu\n",
-		__func__, buf, buflen, npages, args.acl_len);
+	dprintk("%s  buf %p buflen %zu args.acl_len %zu\n",
+		__func__, buf, buflen, args.acl_len);
 	ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode),
 			     &msg, &args.seq_args, &res.seq_res, 0);
 	if (ret)
@@ -4774,7 +4764,7 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
 out_ok:
 	ret = res.acl_len;
 out_free:
-	for (i = 0; i < npages; i++)
+	for (i = 0; i < ARRAY_SIZE(pages) && pages[i]; i++)
 		if (pages[i])
 			__free_page(pages[i]);
 	if (res.acl_scratch)
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index dfed4f5c8fcc..35d15004b0d6 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -5298,8 +5298,6 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
 	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
 		goto out;
 
-	xdr_enter_page(xdr, xdr->buf->page_len);
-
 	/* Calculate the offset of the page data */
 	pg_offset = xdr->buf->head[0].iov_len;
 
-- 
2.5.0

Re: [PATCH] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Trond Myklebust]

On Mon, Dec 14, 2015 at 5:21 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> From: Weston Andros Adamson <dros@netapp.com>
>
> Fix a bug where getxattr returns ERANGE when the attr buffer
> length is close enough to the nearest PAGE_SIZE multiple that adding
> the extra bytes leaves too little room for the ACL buffer.
>
> Besides storing the ACL buffer, the getacl decoder uses the inline
> pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
> must allocate enough page space for all of the data to be decoded.
>
> This patch uses xdr_partial_copy_from_skb to allocate any needed
> pages past the first one. This allows the client to always cache the acl
> on the first getacl call and not just if it fits in one page.
>
> Signed-off-by: Weston Andros Adamson <dros@netapp.com>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>

The thread ends with:

"Indeed, buf->page_len is still set to the maximum number of bytes in
the pages array (set by xdr_inline_pages to tell xdr layer the max
allocation size), and not the number of bytes that are actually
present.

Working on a fix.

-dros"

So no, I'm not taking this patch until someone fixes the issues
identified in the review.

Cheers
  Trond

Re: [PATCH] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[J. Bruce Fields]

On Mon, Dec 14, 2015 at 06:27:20PM -0500, Trond Myklebust wrote:
> On Mon, Dec 14, 2015 at 5:21 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > From: Weston Andros Adamson <dros@netapp.com>
> >
> > Fix a bug where getxattr returns ERANGE when the attr buffer
> > length is close enough to the nearest PAGE_SIZE multiple that adding
> > the extra bytes leaves too little room for the ACL buffer.
> >
> > Besides storing the ACL buffer, the getacl decoder uses the inline
> > pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
> > must allocate enough page space for all of the data to be decoded.
> >
> > This patch uses xdr_partial_copy_from_skb to allocate any needed
> > pages past the first one. This allows the client to always cache the acl
> > on the first getacl call and not just if it fits in one page.
> >
> > Signed-off-by: Weston Andros Adamson <dros@netapp.com>
> > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> The thread ends with:
> 
> "Indeed, buf->page_len is still set to the maximum number of bytes in
> the pages array (set by xdr_inline_pages to tell xdr layer the max
> allocation size), and not the number of bytes that are actually
> present.
> 
> Working on a fix.

Oh, apologies, for some reason I misfiled the rest of that thread.  But
I see it in online archives.  I'll take a look....

--b.

Re: [PATCH] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[J. Bruce Fields]

On Mon, Dec 14, 2015 at 06:27:20PM -0500, Trond Myklebust wrote:
> On Mon, Dec 14, 2015 at 5:21 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > From: Weston Andros Adamson <dros@netapp.com>
> >
> > Fix a bug where getxattr returns ERANGE when the attr buffer
> > length is close enough to the nearest PAGE_SIZE multiple that adding
> > the extra bytes leaves too little room for the ACL buffer.
> >
> > Besides storing the ACL buffer, the getacl decoder uses the inline
> > pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
> > must allocate enough page space for all of the data to be decoded.
> >
> > This patch uses xdr_partial_copy_from_skb to allocate any needed
> > pages past the first one. This allows the client to always cache the acl
> > on the first getacl call and not just if it fits in one page.
> >
> > Signed-off-by: Weston Andros Adamson <dros@netapp.com>
> > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> The thread ends with:
> 
> "Indeed, buf->page_len is still set to the maximum number of bytes in
> the pages array (set by xdr_inline_pages to tell xdr layer the max
> allocation size), and not the number of bytes that are actually
> present.
> 
> Working on a fix.
> 
> -dros"

Dros, do you have a reliable reproducer for the BUG you were seeing?
I'm not having any luck.

--b.

Re: [PATCH] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Jeff Layton]

On Wed, 23 Dec 2015 11:58:49 -0500
"J. Bruce Fields" <bfields@fieldses.org> wrote:

> On Mon, Dec 14, 2015 at 06:27:20PM -0500, Trond Myklebust wrote:
> > On Mon, Dec 14, 2015 at 5:21 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > > From: Weston Andros Adamson <dros@netapp.com>
> > >
> > > Fix a bug where getxattr returns ERANGE when the attr buffer
> > > length is close enough to the nearest PAGE_SIZE multiple that adding
> > > the extra bytes leaves too little room for the ACL buffer.
> > >
> > > Besides storing the ACL buffer, the getacl decoder uses the inline
> > > pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
> > > must allocate enough page space for all of the data to be decoded.
> > >
> > > This patch uses xdr_partial_copy_from_skb to allocate any needed
> > > pages past the first one. This allows the client to always cache the acl
> > > on the first getacl call and not just if it fits in one page.
> > >
> > > Signed-off-by: Weston Andros Adamson <dros@netapp.com>
> > > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> > 
> > The thread ends with:
> > 
> > "Indeed, buf->page_len is still set to the maximum number of bytes in
> > the pages array (set by xdr_inline_pages to tell xdr layer the max
> > allocation size), and not the number of bytes that are actually
> > present.
> > 
> > Working on a fix.
> > 
> > -dros"
> 
> Dros, do you have a reliable reproducer for the BUG you were seeing?
> I'm not having any luck.
> 
> --b.

I doubt Dros' netapp email addr still works. Sending to his PD one...

-- 
Jeff Layton <jeff.layton@primarydata.com>

Re: [PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Weston Andros Adamson]

I’ll update the bugzilla and ask redhat to backport this once it’s accepted by Trond.

-dros

On Nov 27, 2013, at 3:43 AM, Albert Fluegel <af@muc.de> wrote:

> Hi,
> 
> sorry, i missed and deleted this posting from Weston Andros Adamson:
> http://www.spinics.net/lists/linux-nfs/msg40622.html
> so i cannot directly reply anymore. Apologies for messing up the mail
> threads a bit.
> 
> I reported this issue to Redhat 2012-10-25, please see here:
> https://bugzilla.redhat.com/show_bug.cgi?id=869942
> and suggested a fix. I'd greatly appreciate, if someone could confirm
> to Redhat, that the problem and the approach to fix that is basically the
> same, so they'll hopefully backport the patch.
> 
> Thank you very much,
> Albert
> 
> -- 
> Albert Flügel
> Lindwurmstraße 51
> 80337 München
> Telefon: +49-89-2010895
> Telefon: +49-170-5665444
> E-Mail: af@muc.de
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Re: [PATCH v2] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Albert Fluegel]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=unknown-8bit, Size: 823 bytes --]

Hi,

sorry, i missed and deleted this posting from Weston Andros Adamson:
http://www.spinics.net/lists/linux-nfs/msg40622.html
so i cannot directly reply anymore. Apologies for messing up the mail
threads a bit.

I reported this issue to Redhat 2012-10-25, please see here:
https://bugzilla.redhat.com/show_bug.cgi?id=869942
and suggested a fix. I'd greatly appreciate, if someone could confirm
to Redhat, that the problem and the approach to fix that is basically the
same, so they'll hopefully backport the patch.

Thank you very much,
 Albert

-- 
Albert Flügel
Lindwurmstraße 51
80337 München
Telefon: +49-89-2010895
Telefon: +49-170-5665444
E-Mail: af@muc.de
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~ jslwkerbiS4kjaZoifUSDfaworu394kjKLw728K2L1NlwkNSD8 ~~~~~~~~~~~~~