diff mbox

[RFC,v3,36/45] NFSv4: Fix GETATTR bitmap verification

Message ID 8d601ee8babe5239b7926542c713c58502b15e35.1429868795.git.agruenba@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Andreas Grünbacher April 24, 2015, 11:04 a.m. UTC 
The NFSv4 client sends the server GETATTR requests with different sets of
requested attributes depending on the situation.  The requested set of
attributes is encoded in a bitmap; the server replies with the set of
attributes it could return.  These bitmaps can be several words wide.  The
bitmap returned by the server is a subset of the bitmap sent by the client.

While decoding the reply, the client tries to verify the reply bitmap: it
checks if any previous, unexpected attributes are left in the same word of the
bitmap for each attribute it tries to decode, then it clears the current
attribute's bit in the bitmap for the next decode function.

The client fails to detect when unexpected attributes are sent after the last
expected attribute in each word in the bitmap.

Fix this by checking the entire bitmap for unexpected attributes first.  The
server can still send attributes which the client understands but which it
didn't request; this doesn't cause any harm.

Because we don't verify the bitmap one bit at a time anymore, there is no need
for clearing bitmap bits anymore.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/nfs/nfs4xdr.c | 186 +++++++++++++++++++------------------------------------
 1 file changed, 63 insertions(+), 123 deletions(-)

Comments

J. Bruce Fields May 28, 2015, 8:33 p.m. UTC | #1 
On Fri, Apr 24, 2015 at 01:04:33PM +0200, Andreas Gruenbacher wrote:
> The NFSv4 client sends the server GETATTR requests with different sets of
> requested attributes depending on the situation.  The requested set of
> attributes is encoded in a bitmap; the server replies with the set of
> attributes it could return.  These bitmaps can be several words wide.  The
> bitmap returned by the server is a subset of the bitmap sent by the client.
> 
> While decoding the reply, the client tries to verify the reply bitmap: it
> checks if any previous, unexpected attributes are left in the same word of the
> bitmap for each attribute it tries to decode, then it clears the current
> attribute's bit in the bitmap for the next decode function.
> 
> The client fails to detect when unexpected attributes are sent after the last
> expected attribute in each word in the bitmap.

Is it important that the client catch that?

> Fix this by checking the entire bitmap for unexpected attributes first.  The
> server can still send attributes which the client understands but which it
> didn't request; this doesn't cause any harm.

I don't understand that last sentence.  On a skim it looks like after
this patch we *will* still error out if a server does that, right?  (As
we should, that would be a server bug.)

...
> +static int verify_attrs_allowed(uint32_t *bitmap, const uint32_t *attrs_allowed)
> +{
> +	if (unlikely(bitmap[0] & ~attrs_allowed[0] ||
> +		     bitmap[1] & ~attrs_allowed[1] ||
> +		     bitmap[2] & ~attrs_allowed[2]))
> +		return -EIO;
> +	return 0;
> +}
> +
>  static int decode_change_info(struct xdr_stream *xdr, struct nfs4_change_info *cinfo)
>  {
>  	__be32 *p;
> @@ -4296,6 +4195,11 @@ out_overflow:
>  
>  static int decode_server_caps(struct xdr_stream *xdr, struct nfs4_server_caps_res *res)
>  {
> +	static const uint32_t attrs_allowed[3] = {
> +		[0] = FATTR4_WORD0_SUPPORTED_ATTRS | FATTR4_WORD0_FH_EXPIRE_TYPE |
> +		      FATTR4_WORD0_LINK_SUPPORT | FATTR4_WORD0_SYMLINK_SUPPORT |
> +		      FATTR4_WORD0_ACLSUPPORT,
> +	};

This is the same list as in nfs4-xdr_enc_server_caps.  Could we avoid
that duplication?

--b.
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Trond Myklebust May 28, 2015, 8:50 p.m. UTC | #2 
On Thu, May 28, 2015 at 4:33 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> On Fri, Apr 24, 2015 at 01:04:33PM +0200, Andreas Gruenbacher wrote:
>> The NFSv4 client sends the server GETATTR requests with different sets of
>> requested attributes depending on the situation.  The requested set of
>> attributes is encoded in a bitmap; the server replies with the set of
>> attributes it could return.  These bitmaps can be several words wide.  The
>> bitmap returned by the server is a subset of the bitmap sent by the client.
>>
>> While decoding the reply, the client tries to verify the reply bitmap: it
>> checks if any previous, unexpected attributes are left in the same word of the
>> bitmap for each attribute it tries to decode, then it clears the current
>> attribute's bit in the bitmap for the next decode function.
>>
>> The client fails to detect when unexpected attributes are sent after the last
>> expected attribute in each word in the bitmap.
>
> Is it important that the client catch that?

Right. What is the actual problem or bug that this patch is trying to
fix? Why do we care if a buggy server sends us extra info that we
didn't ask for?

Trond
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Andreas Grünbacher May 28, 2015, 9:05 p.m. UTC | #3 
2015-05-28 22:50 GMT+02:00 Trond Myklebust <trond.myklebust@primarydata.com>:
> On Thu, May 28, 2015 at 4:33 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
>> On Fri, Apr 24, 2015 at 01:04:33PM +0200, Andreas Gruenbacher wrote:
>>> The NFSv4 client sends the server GETATTR requests with different sets of
>>> requested attributes depending on the situation.  The requested set of
>>> attributes is encoded in a bitmap; the server replies with the set of
>>> attributes it could return.  These bitmaps can be several words wide.  The
>>> bitmap returned by the server is a subset of the bitmap sent by the client.
>>>
>>> While decoding the reply, the client tries to verify the reply bitmap: it
>>> checks if any previous, unexpected attributes are left in the same word of the
>>> bitmap for each attribute it tries to decode, then it clears the current
>>> attribute's bit in the bitmap for the next decode function.
>>>
>>> The client fails to detect when unexpected attributes are sent after the last
>>> expected attribute in each word in the bitmap.
>>
>> Is it important that the client catch that?
>
> Right. What is the actual problem or bug that this patch is trying to
> fix? Why do we care if a buggy server sends us extra info that we
> didn't ask for?

I think we do care to correctly decode (and reject) well-formed but illegal
server replies. In this case, when switching to the next word of a bitmap, the
client doesn't check if the previous word has been completely "consumed" yet.
If any attributes are "missed", decoding the attribute values gets out of sync,
garbage is decoded, and the error may be missed.

Andreas
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Andreas Grünbacher May 28, 2015, 9:15 p.m. UTC | #4 
2015-05-28 22:33 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>:
> On Fri, Apr 24, 2015 at 01:04:33PM +0200, Andreas Gruenbacher wrote:
>> The client fails to detect when unexpected attributes are sent after the last
>> expected attribute in each word in the bitmap.
>
> Is it important that the client catch that?

Yes if there are more attributes in the next word that the client cares about;
probably no otherwise.

>> Fix this by checking the entire bitmap for unexpected attributes first.  The
>> server can still send attributes which the client understands but which it
>> didn't request; this doesn't cause any harm.
>
> I don't understand that last sentence.  On a skim it looks like after
> this patch we *will* still error out if a server does that, right?  (As
> we should, that would be a server bug.)

We don't actually verify the request bitmap against the reply bitmap;
we don't keep
the request bitmap around long enough. Some decode functions understand a set
of attributes. Currently, we happily accept any of the attributes the
decode function
in question accepts, even ones that were not requested. That could be fixed by
checking the request bitmap against the reply bitmap as well of course.

Andreas
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Andreas Grünbacher May 28, 2015, 9:28 p.m. UTC | #5 
2015-05-28 22:33 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>:
> This is the same list as in nfs4-xdr_enc_server_caps.  Could we avoid
> that duplication?

I don't think it matters at all.

Thanks,
Andreas
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Trond Myklebust May 28, 2015, 9:40 p.m. UTC | #6 
On Thu, May 28, 2015 at 5:05 PM, Andreas Grünbacher
<andreas.gruenbacher@gmail.com> wrote:
> 2015-05-28 22:50 GMT+02:00 Trond Myklebust <trond.myklebust@primarydata.com>:
>> On Thu, May 28, 2015 at 4:33 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
>>> On Fri, Apr 24, 2015 at 01:04:33PM +0200, Andreas Gruenbacher wrote:
>>>> The NFSv4 client sends the server GETATTR requests with different sets of
>>>> requested attributes depending on the situation.  The requested set of
>>>> attributes is encoded in a bitmap; the server replies with the set of
>>>> attributes it could return.  These bitmaps can be several words wide.  The
>>>> bitmap returned by the server is a subset of the bitmap sent by the client.
>>>>
>>>> While decoding the reply, the client tries to verify the reply bitmap: it
>>>> checks if any previous, unexpected attributes are left in the same word of the
>>>> bitmap for each attribute it tries to decode, then it clears the current
>>>> attribute's bit in the bitmap for the next decode function.
>>>>
>>>> The client fails to detect when unexpected attributes are sent after the last
>>>> expected attribute in each word in the bitmap.
>>>
>>> Is it important that the client catch that?
>>
>> Right. What is the actual problem or bug that this patch is trying to
>> fix? Why do we care if a buggy server sends us extra info that we
>> didn't ask for?
>
> I think we do care to correctly decode (and reject) well-formed but illegal
> server replies. In this case, when switching to the next word of a bitmap, the
> client doesn't check if the previous word has been completely "consumed" yet.
> If any attributes are "missed", decoding the attribute values gets out of sync,
> garbage is decoded, and the error may be missed.
>

We already do this kind of check with the existing code. What's wrong with it?

Trond
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Trond Myklebust May 28, 2015, 9:55 p.m. UTC | #7 
On Thu, May 28, 2015 at 5:40 PM, Trond Myklebust
<trond.myklebust@primarydata.com> wrote:
> On Thu, May 28, 2015 at 5:05 PM, Andreas Grünbacher
> <andreas.gruenbacher@gmail.com> wrote:
>> 2015-05-28 22:50 GMT+02:00 Trond Myklebust <trond.myklebust@primarydata.com>:
>>> On Thu, May 28, 2015 at 4:33 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
>>>> On Fri, Apr 24, 2015 at 01:04:33PM +0200, Andreas Gruenbacher wrote:
>>>>> The NFSv4 client sends the server GETATTR requests with different sets of
>>>>> requested attributes depending on the situation.  The requested set of
>>>>> attributes is encoded in a bitmap; the server replies with the set of
>>>>> attributes it could return.  These bitmaps can be several words wide.  The
>>>>> bitmap returned by the server is a subset of the bitmap sent by the client.
>>>>>
>>>>> While decoding the reply, the client tries to verify the reply bitmap: it
>>>>> checks if any previous, unexpected attributes are left in the same word of the
>>>>> bitmap for each attribute it tries to decode, then it clears the current
>>>>> attribute's bit in the bitmap for the next decode function.
>>>>>
>>>>> The client fails to detect when unexpected attributes are sent after the last
>>>>> expected attribute in each word in the bitmap.
>>>>
>>>> Is it important that the client catch that?
>>>
>>> Right. What is the actual problem or bug that this patch is trying to
>>> fix? Why do we care if a buggy server sends us extra info that we
>>> didn't ask for?
>>
>> I think we do care to correctly decode (and reject) well-formed but illegal
>> server replies. In this case, when switching to the next word of a bitmap, the
>> client doesn't check if the previous word has been completely "consumed" yet.
>> If any attributes are "missed", decoding the attribute values gets out of sync,
>> garbage is decoded, and the error may be missed.
>>
>
> We already do this kind of check with the existing code. What's wrong with it?
>

Actually, you're right, we don't check for the previous word, however
fixing that is a question of adding 2 extra checks in
decode_getfattr_attrs(), one in decode_getfattr_statfs(), and one in
decode_fsinfo().

It shouldn't require a rewrite of the entire nfs4xdr.c.

Trond
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Andreas Grünbacher May 28, 2015, 10:09 p.m. UTC | #8 
2015-05-28 23:55 GMT+02:00 Trond Myklebust <trond.myklebust@primarydata.com>:
>> We already do this kind of check with the existing code. What's wrong with it?
>
> Actually, you're right, we don't check for the previous word, however
> fixing that is a question of adding 2 extra checks in
> decode_getfattr_attrs(), one in decode_getfattr_statfs(), and one in
> decode_fsinfo().
>
> It shouldn't require a rewrite of the entire nfs4xdr.c.

I would actually prefer either verifying the reply bitmap against the
request bitmap,
or checking the bitmap first as this patch does --- the current
approach of knocking
individual bits over and checking if any "before" bits have been missed isn't
exactly what I would take as a textbook example.

Thanks,
Andreas
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Trond Myklebust May 28, 2015, 10:24 p.m. UTC | #9 
On Thu, May 28, 2015 at 6:09 PM, Andreas Grünbacher
<andreas.gruenbacher@gmail.com> wrote:
> 2015-05-28 23:55 GMT+02:00 Trond Myklebust <trond.myklebust@primarydata.com>:
>>> We already do this kind of check with the existing code. What's wrong with it?
>>
>> Actually, you're right, we don't check for the previous word, however
>> fixing that is a question of adding 2 extra checks in
>> decode_getfattr_attrs(), one in decode_getfattr_statfs(), and one in
>> decode_fsinfo().
>>
>> It shouldn't require a rewrite of the entire nfs4xdr.c.
>
> I would actually prefer either verifying the reply bitmap against the
> request bitmap,
> or checking the bitmap first as this patch does --- the current
> approach of knocking
> individual bits over and checking if any "before" bits have been missed isn't
> exactly what I would take as a textbook example.


...and I'd prefer that we don't keep rewriting code that works. Screw
the textbooks...

Trond
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Andreas Grünbacher May 28, 2015, 10:28 p.m. UTC | #10 
2015-05-29 0:24 GMT+02:00 Trond Myklebust <trond.myklebust@primarydata.com>:
> ...and I'd prefer that we don't keep rewriting code that works.

Sure, go ahead.

Thanks,
Andreas
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 5c399ec..36b5e95 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -3151,7 +3151,6 @@  static int decode_attr_supported(struct xdr_stream *xdr, uint32_t *bitmap, uint3
 		ret = decode_attr_bitmap(xdr, bitmask);
 		if (unlikely(ret < 0))
 			return ret;
-		bitmap[0] &= ~FATTR4_WORD0_SUPPORTED_ATTRS;
 	} else
 		bitmask[0] = bitmask[1] = bitmask[2] = 0;
 	dprintk("%s: bitmask=%08x:%08x:%08x\n", __func__,
@@ -3165,8 +3164,6 @@  static int decode_attr_type(struct xdr_stream *xdr, uint32_t *bitmap, uint32_t *
 	int ret = 0;
 
 	*type = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_TYPE - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_TYPE)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
@@ -3176,7 +3173,6 @@  static int decode_attr_type(struct xdr_stream *xdr, uint32_t *bitmap, uint32_t *
 			dprintk("%s: bad type %d\n", __func__, *type);
 			return -EIO;
 		}
-		bitmap[0] &= ~FATTR4_WORD0_TYPE;
 		ret = NFS_ATTR_FATTR_TYPE;
 	}
 	dprintk("%s: type=0%o\n", __func__, nfs_type2fmt[*type]);
@@ -3192,14 +3188,11 @@  static int decode_attr_fh_expire_type(struct xdr_stream *xdr,
 	__be32 *p;
 
 	*type = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_FH_EXPIRE_TYPE - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_FH_EXPIRE_TYPE)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		*type = be32_to_cpup(p);
-		bitmap[0] &= ~FATTR4_WORD0_FH_EXPIRE_TYPE;
 	}
 	dprintk("%s: expire type=0x%x\n", __func__, *type);
 	return 0;
@@ -3214,14 +3207,11 @@  static int decode_attr_change(struct xdr_stream *xdr, uint32_t *bitmap, uint64_t
 	int ret = 0;
 
 	*change = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_CHANGE - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_CHANGE)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, change);
-		bitmap[0] &= ~FATTR4_WORD0_CHANGE;
 		ret = NFS_ATTR_FATTR_CHANGE;
 	}
 	dprintk("%s: change attribute=%Lu\n", __func__,
@@ -3238,14 +3228,11 @@  static int decode_attr_size(struct xdr_stream *xdr, uint32_t *bitmap, uint64_t *
 	int ret = 0;
 
 	*size = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_SIZE - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_SIZE)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, size);
-		bitmap[0] &= ~FATTR4_WORD0_SIZE;
 		ret = NFS_ATTR_FATTR_SIZE;
 	}
 	dprintk("%s: file size=%Lu\n", __func__, (unsigned long long)*size);
@@ -3260,14 +3247,11 @@  static int decode_attr_link_support(struct xdr_stream *xdr, uint32_t *bitmap, ui
 	__be32 *p;
 
 	*res = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_LINK_SUPPORT - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_LINK_SUPPORT)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		*res = be32_to_cpup(p);
-		bitmap[0] &= ~FATTR4_WORD0_LINK_SUPPORT;
 	}
 	dprintk("%s: link support=%s\n", __func__, *res == 0 ? "false" : "true");
 	return 0;
@@ -3281,14 +3265,11 @@  static int decode_attr_symlink_support(struct xdr_stream *xdr, uint32_t *bitmap,
 	__be32 *p;
 
 	*res = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_SYMLINK_SUPPORT - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_SYMLINK_SUPPORT)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		*res = be32_to_cpup(p);
-		bitmap[0] &= ~FATTR4_WORD0_SYMLINK_SUPPORT;
 	}
 	dprintk("%s: symlink support=%s\n", __func__, *res == 0 ? "false" : "true");
 	return 0;
@@ -3304,15 +3285,12 @@  static int decode_attr_fsid(struct xdr_stream *xdr, uint32_t *bitmap, struct nfs
 
 	fsid->major = 0;
 	fsid->minor = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_FSID - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_FSID)) {
 		p = xdr_inline_decode(xdr, 16);
 		if (unlikely(!p))
 			goto out_overflow;
 		p = xdr_decode_hyper(p, &fsid->major);
 		xdr_decode_hyper(p, &fsid->minor);
-		bitmap[0] &= ~FATTR4_WORD0_FSID;
 		ret = NFS_ATTR_FATTR_FSID;
 	}
 	dprintk("%s: fsid=(0x%Lx/0x%Lx)\n", __func__,
@@ -3329,14 +3307,11 @@  static int decode_attr_lease_time(struct xdr_stream *xdr, uint32_t *bitmap, uint
 	__be32 *p;
 
 	*res = 60;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_LEASE_TIME - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_LEASE_TIME)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		*res = be32_to_cpup(p);
-		bitmap[0] &= ~FATTR4_WORD0_LEASE_TIME;
 	}
 	dprintk("%s: file size=%u\n", __func__, (unsigned int)*res);
 	return 0;
@@ -3349,13 +3324,10 @@  static int decode_attr_error(struct xdr_stream *xdr, uint32_t *bitmap, int32_t *
 {
 	__be32 *p;
 
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_RDATTR_ERROR - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_RDATTR_ERROR)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
-		bitmap[0] &= ~FATTR4_WORD0_RDATTR_ERROR;
 		*res = -be32_to_cpup(p);
 	}
 	return 0;
@@ -3372,8 +3344,6 @@  static int decode_attr_filehandle(struct xdr_stream *xdr, uint32_t *bitmap, stru
 	if (fh != NULL)
 		memset(fh, 0, sizeof(*fh));
 
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_FILEHANDLE - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_FILEHANDLE)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
@@ -3388,7 +3358,6 @@  static int decode_attr_filehandle(struct xdr_stream *xdr, uint32_t *bitmap, stru
 			memcpy(fh->data, p, len);
 			fh->size = len;
 		}
-		bitmap[0] &= ~FATTR4_WORD0_FILEHANDLE;
 	}
 	return 0;
 out_overflow:
@@ -3401,14 +3370,11 @@  static int decode_attr_aclsupport(struct xdr_stream *xdr, uint32_t *bitmap, uint
 	__be32 *p;
 
 	*res = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_ACLSUPPORT - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_ACLSUPPORT)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		*res = be32_to_cpup(p);
-		bitmap[0] &= ~FATTR4_WORD0_ACLSUPPORT;
 	}
 	dprintk("%s: ACLs supported=%u\n", __func__, (unsigned int)*res);
 	return 0;
@@ -3423,14 +3389,11 @@  static int decode_attr_fileid(struct xdr_stream *xdr, uint32_t *bitmap, uint64_t
 	int ret = 0;
 
 	*fileid = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_FILEID - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_FILEID)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, fileid);
-		bitmap[0] &= ~FATTR4_WORD0_FILEID;
 		ret = NFS_ATTR_FATTR_FILEID;
 	}
 	dprintk("%s: fileid=%Lu\n", __func__, (unsigned long long)*fileid);
@@ -3446,14 +3409,11 @@  static int decode_attr_mounted_on_fileid(struct xdr_stream *xdr, uint32_t *bitma
 	int ret = 0;
 
 	*fileid = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_MOUNTED_ON_FILEID - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_MOUNTED_ON_FILEID)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, fileid);
-		bitmap[1] &= ~FATTR4_WORD1_MOUNTED_ON_FILEID;
 		ret = NFS_ATTR_FATTR_MOUNTED_ON_FILEID;
 	}
 	dprintk("%s: fileid=%Lu\n", __func__, (unsigned long long)*fileid);
@@ -3469,14 +3429,11 @@  static int decode_attr_files_avail(struct xdr_stream *xdr, uint32_t *bitmap, uin
 	int status = 0;
 
 	*res = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_FILES_AVAIL - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_FILES_AVAIL)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, res);
-		bitmap[0] &= ~FATTR4_WORD0_FILES_AVAIL;
 	}
 	dprintk("%s: files avail=%Lu\n", __func__, (unsigned long long)*res);
 	return status;
@@ -3491,14 +3448,11 @@  static int decode_attr_files_free(struct xdr_stream *xdr, uint32_t *bitmap, uint
 	int status = 0;
 
 	*res = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_FILES_FREE - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_FILES_FREE)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, res);
-		bitmap[0] &= ~FATTR4_WORD0_FILES_FREE;
 	}
 	dprintk("%s: files free=%Lu\n", __func__, (unsigned long long)*res);
 	return status;
@@ -3513,14 +3467,11 @@  static int decode_attr_files_total(struct xdr_stream *xdr, uint32_t *bitmap, uin
 	int status = 0;
 
 	*res = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_FILES_TOTAL - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_FILES_TOTAL)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, res);
-		bitmap[0] &= ~FATTR4_WORD0_FILES_TOTAL;
 	}
 	dprintk("%s: files total=%Lu\n", __func__, (unsigned long long)*res);
 	return status;
@@ -3578,11 +3529,8 @@  static int decode_attr_fs_locations(struct xdr_stream *xdr, uint32_t *bitmap, st
 {
 	int n;
 	__be32 *p;
-	int status = -EIO;
+	int status = 0;
 
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_FS_LOCATIONS -1U)))
-		goto out;
-	status = 0;
 	if (unlikely(!(bitmap[0] & FATTR4_WORD0_FS_LOCATIONS)))
 		goto out;
 	status = -EIO;
@@ -3659,14 +3607,11 @@  static int decode_attr_maxfilesize(struct xdr_stream *xdr, uint32_t *bitmap, uin
 	int status = 0;
 
 	*res = 0;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_MAXFILESIZE - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_MAXFILESIZE)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, res);
-		bitmap[0] &= ~FATTR4_WORD0_MAXFILESIZE;
 	}
 	dprintk("%s: maxfilesize=%Lu\n", __func__, (unsigned long long)*res);
 	return status;
@@ -3681,14 +3626,11 @@  static int decode_attr_maxlink(struct xdr_stream *xdr, uint32_t *bitmap, uint32_
 	int status = 0;
 
 	*maxlink = 1;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_MAXLINK - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_MAXLINK)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		*maxlink = be32_to_cpup(p);
-		bitmap[0] &= ~FATTR4_WORD0_MAXLINK;
 	}
 	dprintk("%s: maxlink=%u\n", __func__, *maxlink);
 	return status;
@@ -3703,14 +3645,11 @@  static int decode_attr_maxname(struct xdr_stream *xdr, uint32_t *bitmap, uint32_
 	int status = 0;
 
 	*maxname = 1024;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_MAXNAME - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_MAXNAME)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		*maxname = be32_to_cpup(p);
-		bitmap[0] &= ~FATTR4_WORD0_MAXNAME;
 	}
 	dprintk("%s: maxname=%u\n", __func__, *maxname);
 	return status;
@@ -3725,8 +3664,6 @@  static int decode_attr_maxread(struct xdr_stream *xdr, uint32_t *bitmap, uint32_
 	int status = 0;
 
 	*res = 1024;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_MAXREAD - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_MAXREAD)) {
 		uint64_t maxread;
 		p = xdr_inline_decode(xdr, 8);
@@ -3736,7 +3673,6 @@  static int decode_attr_maxread(struct xdr_stream *xdr, uint32_t *bitmap, uint32_
 		if (maxread > 0x7FFFFFFF)
 			maxread = 0x7FFFFFFF;
 		*res = (uint32_t)maxread;
-		bitmap[0] &= ~FATTR4_WORD0_MAXREAD;
 	}
 	dprintk("%s: maxread=%lu\n", __func__, (unsigned long)*res);
 	return status;
@@ -3751,8 +3687,6 @@  static int decode_attr_maxwrite(struct xdr_stream *xdr, uint32_t *bitmap, uint32
 	int status = 0;
 
 	*res = 1024;
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_MAXWRITE - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_MAXWRITE)) {
 		uint64_t maxwrite;
 		p = xdr_inline_decode(xdr, 8);
@@ -3762,7 +3696,6 @@  static int decode_attr_maxwrite(struct xdr_stream *xdr, uint32_t *bitmap, uint32
 		if (maxwrite > 0x7FFFFFFF)
 			maxwrite = 0x7FFFFFFF;
 		*res = (uint32_t)maxwrite;
-		bitmap[0] &= ~FATTR4_WORD0_MAXWRITE;
 	}
 	dprintk("%s: maxwrite=%lu\n", __func__, (unsigned long)*res);
 	return status;
@@ -3778,15 +3711,12 @@  static int decode_attr_mode(struct xdr_stream *xdr, uint32_t *bitmap, umode_t *m
 	int ret = 0;
 
 	*mode = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_MODE - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_MODE)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		tmp = be32_to_cpup(p);
 		*mode = tmp & ~S_IFMT;
-		bitmap[1] &= ~FATTR4_WORD1_MODE;
 		ret = NFS_ATTR_FATTR_MODE;
 	}
 	dprintk("%s: file mode=0%o\n", __func__, (unsigned int)*mode);
@@ -3802,14 +3732,11 @@  static int decode_attr_nlink(struct xdr_stream *xdr, uint32_t *bitmap, uint32_t
 	int ret = 0;
 
 	*nlink = 1;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_NUMLINKS - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_NUMLINKS)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
 			goto out_overflow;
 		*nlink = be32_to_cpup(p);
-		bitmap[1] &= ~FATTR4_WORD1_NUMLINKS;
 		ret = NFS_ATTR_FATTR_NLINK;
 	}
 	dprintk("%s: nlink=%u\n", __func__, (unsigned int)*nlink);
@@ -3828,8 +3755,6 @@  static int decode_attr_owner(struct xdr_stream *xdr, uint32_t *bitmap,
 	int ret = 0;
 
 	*uid = make_kuid(&init_user_ns, -2);
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_OWNER - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_OWNER)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
@@ -3853,7 +3778,6 @@  static int decode_attr_owner(struct xdr_stream *xdr, uint32_t *bitmap,
 		} else
 			dprintk("%s: name too long (%u)!\n",
 					__func__, len);
-		bitmap[1] &= ~FATTR4_WORD1_OWNER;
 	}
 	dprintk("%s: uid=%d\n", __func__, (int)from_kuid(&init_user_ns, *uid));
 	return ret;
@@ -3871,8 +3795,6 @@  static int decode_attr_group(struct xdr_stream *xdr, uint32_t *bitmap,
 	int ret = 0;
 
 	*gid = make_kgid(&init_user_ns, -2);
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_OWNER_GROUP - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_OWNER_GROUP)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
@@ -3896,7 +3818,6 @@  static int decode_attr_group(struct xdr_stream *xdr, uint32_t *bitmap,
 		} else
 			dprintk("%s: name too long (%u)!\n",
 					__func__, len);
-		bitmap[1] &= ~FATTR4_WORD1_OWNER_GROUP;
 	}
 	dprintk("%s: gid=%d\n", __func__, (int)from_kgid(&init_user_ns, *gid));
 	return ret;
@@ -3912,8 +3833,6 @@  static int decode_attr_rdev(struct xdr_stream *xdr, uint32_t *bitmap, dev_t *rde
 	int ret = 0;
 
 	*rdev = MKDEV(0,0);
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_RAWDEV - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_RAWDEV)) {
 		dev_t tmp;
 
@@ -3925,7 +3844,6 @@  static int decode_attr_rdev(struct xdr_stream *xdr, uint32_t *bitmap, dev_t *rde
 		tmp = MKDEV(major, minor);
 		if (MAJOR(tmp) == major && MINOR(tmp) == minor)
 			*rdev = tmp;
-		bitmap[1] &= ~ FATTR4_WORD1_RAWDEV;
 		ret = NFS_ATTR_FATTR_RDEV;
 	}
 	dprintk("%s: rdev=(0x%x:0x%x)\n", __func__, major, minor);
@@ -3941,14 +3859,11 @@  static int decode_attr_space_avail(struct xdr_stream *xdr, uint32_t *bitmap, uin
 	int status = 0;
 
 	*res = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_SPACE_AVAIL - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_SPACE_AVAIL)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, res);
-		bitmap[1] &= ~FATTR4_WORD1_SPACE_AVAIL;
 	}
 	dprintk("%s: space avail=%Lu\n", __func__, (unsigned long long)*res);
 	return status;
@@ -3963,14 +3878,11 @@  static int decode_attr_space_free(struct xdr_stream *xdr, uint32_t *bitmap, uint
 	int status = 0;
 
 	*res = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_SPACE_FREE - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_SPACE_FREE)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, res);
-		bitmap[1] &= ~FATTR4_WORD1_SPACE_FREE;
 	}
 	dprintk("%s: space free=%Lu\n", __func__, (unsigned long long)*res);
 	return status;
@@ -3985,14 +3897,11 @@  static int decode_attr_space_total(struct xdr_stream *xdr, uint32_t *bitmap, uin
 	int status = 0;
 
 	*res = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_SPACE_TOTAL - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_SPACE_TOTAL)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, res);
-		bitmap[1] &= ~FATTR4_WORD1_SPACE_TOTAL;
 	}
 	dprintk("%s: space total=%Lu\n", __func__, (unsigned long long)*res);
 	return status;
@@ -4007,14 +3916,11 @@  static int decode_attr_space_used(struct xdr_stream *xdr, uint32_t *bitmap, uint
 	int ret = 0;
 
 	*used = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_SPACE_USED - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_SPACE_USED)) {
 		p = xdr_inline_decode(xdr, 8);
 		if (unlikely(!p))
 			goto out_overflow;
 		xdr_decode_hyper(p, used);
-		bitmap[1] &= ~FATTR4_WORD1_SPACE_USED;
 		ret = NFS_ATTR_FATTR_SPACE_USED;
 	}
 	dprintk("%s: space used=%Lu\n", __func__,
@@ -4050,13 +3956,10 @@  static int decode_attr_time_access(struct xdr_stream *xdr, uint32_t *bitmap, str
 
 	time->tv_sec = 0;
 	time->tv_nsec = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_TIME_ACCESS - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_TIME_ACCESS)) {
 		status = decode_attr_time(xdr, time);
 		if (status == 0)
 			status = NFS_ATTR_FATTR_ATIME;
-		bitmap[1] &= ~FATTR4_WORD1_TIME_ACCESS;
 	}
 	dprintk("%s: atime=%ld\n", __func__, (long)time->tv_sec);
 	return status;
@@ -4068,13 +3971,10 @@  static int decode_attr_time_metadata(struct xdr_stream *xdr, uint32_t *bitmap, s
 
 	time->tv_sec = 0;
 	time->tv_nsec = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_TIME_METADATA - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_TIME_METADATA)) {
 		status = decode_attr_time(xdr, time);
 		if (status == 0)
 			status = NFS_ATTR_FATTR_CTIME;
-		bitmap[1] &= ~FATTR4_WORD1_TIME_METADATA;
 	}
 	dprintk("%s: ctime=%ld\n", __func__, (long)time->tv_sec);
 	return status;
@@ -4087,12 +3987,8 @@  static int decode_attr_time_delta(struct xdr_stream *xdr, uint32_t *bitmap,
 
 	time->tv_sec = 0;
 	time->tv_nsec = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_TIME_DELTA - 1U)))
-		return -EIO;
-	if (likely(bitmap[1] & FATTR4_WORD1_TIME_DELTA)) {
+	if (likely(bitmap[1] & FATTR4_WORD1_TIME_DELTA))
 		status = decode_attr_time(xdr, time);
-		bitmap[1] &= ~FATTR4_WORD1_TIME_DELTA;
-	}
 	dprintk("%s: time_delta=%ld %ld\n", __func__, (long)time->tv_sec,
 		(long)time->tv_nsec);
 	return status;
@@ -4107,8 +4003,6 @@  static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
 	__be32 *p;
 	int status = 0;
 
-	if (unlikely(bitmap[2] & (FATTR4_WORD2_SECURITY_LABEL - 1U)))
-		return -EIO;
 	if (likely(bitmap[2] & FATTR4_WORD2_SECURITY_LABEL)) {
 		p = xdr_inline_decode(xdr, 4);
 		if (unlikely(!p))
@@ -4133,7 +4027,6 @@  static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
 				label->lfs = lfs;
 				status = NFS_ATTR_FATTR_V4_SECURITY_LABEL;
 			}
-			bitmap[2] &= ~FATTR4_WORD2_SECURITY_LABEL;
 		} else
 			printk(KERN_WARNING "%s: label too long (%u)!\n",
 					__func__, len);
@@ -4154,13 +4047,10 @@  static int decode_attr_time_modify(struct xdr_stream *xdr, uint32_t *bitmap, str
 
 	time->tv_sec = 0;
 	time->tv_nsec = 0;
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_TIME_MODIFY - 1U)))
-		return -EIO;
 	if (likely(bitmap[1] & FATTR4_WORD1_TIME_MODIFY)) {
 		status = decode_attr_time(xdr, time);
 		if (status == 0)
 			status = NFS_ATTR_FATTR_MTIME;
-		bitmap[1] &= ~FATTR4_WORD1_TIME_MODIFY;
 	}
 	dprintk("%s: mtime=%ld\n", __func__, (long)time->tv_sec);
 	return status;
@@ -4183,6 +4073,15 @@  static int verify_attr_len(struct xdr_stream *xdr, unsigned int savep, uint32_t
 	return 0;
 }
 
+static int verify_attrs_allowed(uint32_t *bitmap, const uint32_t *attrs_allowed)
+{
+	if (unlikely(bitmap[0] & ~attrs_allowed[0] ||
+		     bitmap[1] & ~attrs_allowed[1] ||
+		     bitmap[2] & ~attrs_allowed[2]))
+		return -EIO;
+	return 0;
+}
+
 static int decode_change_info(struct xdr_stream *xdr, struct nfs4_change_info *cinfo)
 {
 	__be32 *p;
@@ -4296,6 +4195,11 @@  out_overflow:
 
 static int decode_server_caps(struct xdr_stream *xdr, struct nfs4_server_caps_res *res)
 {
+	static const uint32_t attrs_allowed[3] = {
+		[0] = FATTR4_WORD0_SUPPORTED_ATTRS | FATTR4_WORD0_FH_EXPIRE_TYPE |
+		      FATTR4_WORD0_LINK_SUPPORT | FATTR4_WORD0_SYMLINK_SUPPORT |
+		      FATTR4_WORD0_ACLSUPPORT,
+	};
 	unsigned int savep;
 	uint32_t attrlen, bitmap[3] = {0};
 	int status;
@@ -4304,6 +4208,8 @@  static int decode_server_caps(struct xdr_stream *xdr, struct nfs4_server_caps_re
 		goto xdr_error;
 	if ((status = decode_attr_bitmap(xdr, bitmap)) != 0)
 		goto xdr_error;
+	if ((status = verify_attrs_allowed(bitmap, attrs_allowed)) != 0)
+		goto xdr_error;
 	if ((status = decode_attr_length(xdr, &attrlen, &savep)) != 0)
 		goto xdr_error;
 	if ((status = decode_attr_supported(xdr, bitmap, res->attr_bitmask)) != 0)
@@ -4325,6 +4231,12 @@  xdr_error:
 
 static int decode_statfs(struct xdr_stream *xdr, struct nfs_fsstat *fsstat)
 {
+	static const uint32_t attrs_allowed[3] = {
+		[0] = FATTR4_WORD0_FILES_AVAIL | FATTR4_WORD0_FILES_FREE |
+		      FATTR4_WORD0_FILES_TOTAL,
+		[1] = FATTR4_WORD1_SPACE_AVAIL | FATTR4_WORD1_SPACE_FREE |
+		      FATTR4_WORD1_SPACE_TOTAL,
+	};
 	unsigned int savep;
 	uint32_t attrlen, bitmap[3] = {0};
 	int status;
@@ -4333,6 +4245,8 @@  static int decode_statfs(struct xdr_stream *xdr, struct nfs_fsstat *fsstat)
 		goto xdr_error;
 	if ((status = decode_attr_bitmap(xdr, bitmap)) != 0)
 		goto xdr_error;
+	if ((status = verify_attrs_allowed(bitmap, attrs_allowed)) != 0)
+		goto xdr_error;
 	if ((status = decode_attr_length(xdr, &attrlen, &savep)) != 0)
 		goto xdr_error;
 
@@ -4357,6 +4271,9 @@  xdr_error:
 
 static int decode_pathconf(struct xdr_stream *xdr, struct nfs_pathconf *pathconf)
 {
+	static const uint32_t attrs_allowed[3] = {
+		[0] = FATTR4_WORD0_MAXLINK | FATTR4_WORD0_MAXNAME,
+	};
 	unsigned int savep;
 	uint32_t attrlen, bitmap[3] = {0};
 	int status;
@@ -4365,6 +4282,8 @@  static int decode_pathconf(struct xdr_stream *xdr, struct nfs_pathconf *pathconf
 		goto xdr_error;
 	if ((status = decode_attr_bitmap(xdr, bitmap)) != 0)
 		goto xdr_error;
+	if ((status = verify_attrs_allowed(bitmap, attrs_allowed)) != 0)
+		goto xdr_error;
 	if ((status = decode_attr_length(xdr, &attrlen, &savep)) != 0)
 		goto xdr_error;
 
@@ -4462,8 +4381,6 @@  static int decode_attr_mdsthreshold(struct xdr_stream *xdr,
 	int status = 0;
 	uint32_t num;
 
-	if (unlikely(bitmap[2] & (FATTR4_WORD2_MDSTHRESHOLD - 1U)))
-		return -EIO;
 	if (bitmap[2] & FATTR4_WORD2_MDSTHRESHOLD) {
 		/* Did the server return an unrequested attribute? */
 		if (unlikely(res == NULL))
@@ -4480,7 +4397,6 @@  static int decode_attr_mdsthreshold(struct xdr_stream *xdr,
 				__func__);
 
 		status = decode_first_threshold_item4(xdr, res);
-		bitmap[2] &= ~FATTR4_WORD2_MDSTHRESHOLD;
 	}
 	return status;
 out_overflow:
@@ -4493,11 +4409,28 @@  static int decode_getfattr_attrs(struct xdr_stream *xdr, uint32_t *bitmap,
 		struct nfs4_fs_locations *fs_loc, struct nfs4_label *label,
 		const struct nfs_server *server)
 {
+	static const uint32_t attrs_allowed[3] = {
+		[0] = FATTR4_WORD0_TYPE | FATTR4_WORD0_CHANGE |
+		      FATTR4_WORD0_SIZE | FATTR4_WORD0_FSID |
+		      FATTR4_WORD0_RDATTR_ERROR | FATTR4_WORD0_FILEHANDLE |
+		      FATTR4_WORD0_FILEID | FATTR4_WORD0_FS_LOCATIONS,
+		[1] = FATTR4_WORD1_MODE | FATTR4_WORD1_NUMLINKS |
+		      FATTR4_WORD1_OWNER | FATTR4_WORD1_OWNER_GROUP |
+		      FATTR4_WORD1_RAWDEV | FATTR4_WORD1_SPACE_USED |
+		      FATTR4_WORD1_TIME_ACCESS | FATTR4_WORD1_TIME_METADATA |
+		      FATTR4_WORD1_TIME_MODIFY |
+		      FATTR4_WORD1_MOUNTED_ON_FILEID,
+		[2] = FATTR4_WORD2_MDSTHRESHOLD | FATTR4_WORD2_SECURITY_LABEL,
+	};
 	int status;
 	umode_t fmode = 0;
 	uint32_t type;
 	int32_t err;
 
+	status = verify_attrs_allowed(bitmap, attrs_allowed);
+	if (status != 0)
+		goto xdr_error;
+
 	status = decode_attr_type(xdr, bitmap, &type);
 	if (status < 0)
 		goto xdr_error;
@@ -4699,12 +4632,9 @@  static int decode_attr_pnfstype(struct xdr_stream *xdr, uint32_t *bitmap,
 	int status = 0;
 
 	dprintk("%s: bitmap is %x\n", __func__, bitmap[1]);
-	if (unlikely(bitmap[1] & (FATTR4_WORD1_FS_LAYOUT_TYPES - 1U)))
-		return -EIO;
-	if (bitmap[1] & FATTR4_WORD1_FS_LAYOUT_TYPES) {
+	if (bitmap[1] & FATTR4_WORD1_FS_LAYOUT_TYPES)
 		status = decode_first_pnfs_layout_type(xdr, layouttype);
-		bitmap[1] &= ~FATTR4_WORD1_FS_LAYOUT_TYPES;
-	} else
+	else
 		*layouttype = 0;
 	return status;
 }
@@ -4726,13 +4656,18 @@  static int decode_attr_layout_blksize(struct xdr_stream *xdr, uint32_t *bitmap,
 			return -EIO;
 		}
 		*res = be32_to_cpup(p);
-		bitmap[2] &= ~FATTR4_WORD2_LAYOUT_BLKSIZE;
 	}
 	return 0;
 }
 
 static int decode_fsinfo(struct xdr_stream *xdr, struct nfs_fsinfo *fsinfo)
 {
+	static const uint32_t attrs_allowed[3] = {
+		[0] = FATTR4_WORD0_LEASE_TIME | FATTR4_WORD0_MAXFILESIZE |
+		      FATTR4_WORD0_MAXREAD | FATTR4_WORD0_MAXWRITE,
+		[1] = FATTR4_WORD1_TIME_DELTA | FATTR4_WORD1_FS_LAYOUT_TYPES,
+		[2] = FATTR4_WORD2_LAYOUT_BLKSIZE,
+	};
 	unsigned int savep;
 	uint32_t attrlen, bitmap[3];
 	int status;
@@ -4741,6 +4676,8 @@  static int decode_fsinfo(struct xdr_stream *xdr, struct nfs_fsinfo *fsinfo)
 		goto xdr_error;
 	if ((status = decode_attr_bitmap(xdr, bitmap)) != 0)
 		goto xdr_error;
+	if ((status = verify_attrs_allowed(bitmap, attrs_allowed) != 0))
+		goto xdr_error;
 	if ((status = decode_attr_length(xdr, &attrlen, &savep)) != 0)
 		goto xdr_error;
 
@@ -5203,6 +5140,9 @@  decode_restorefh(struct xdr_stream *xdr)
 static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
 			 struct nfs_getaclres *res)
 {
+	static const uint32_t attrs_allowed[3] = {
+		[0] = FATTR4_WORD0_ACL,
+	};
 	unsigned int savep;
 	uint32_t attrlen,
 		 bitmap[3] = {0};
@@ -5220,11 +5160,11 @@  static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
 
 	if ((status = decode_attr_bitmap(xdr, bitmap)) != 0)
 		goto out;
+	if ((status = verify_attrs_allowed(bitmap, attrs_allowed)) != 0)
+		goto out;
 	if ((status = decode_attr_length(xdr, &attrlen, &savep)) != 0)
 		goto out;
 
-	if (unlikely(bitmap[0] & (FATTR4_WORD0_ACL - 1U)))
-		return -EIO;
 	if (likely(bitmap[0] & FATTR4_WORD0_ACL)) {
 
 		/* The bitmap (xdr len + bitmaps) and the attr xdr len words