nfsd: Revert "nfsd: check for oversized NFSv2/v3 arguments"

This reverts commit 51f567777799 "nfsd: check for oversized NFSv2/v3
arguments", which breaks support for NFSv3 ACLs.

That patch was actually an earlier draft of a fix for the problem that
was eventually fixed by e6838a29ecb "nfsd: check for oversized NFSv2/v3
arguments".  But somehow I accidentally left this earlier draft in the
branch that was part of my 2.12 pull request.

Reported-by: Eryu Guan <eguan@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs3xdr.c

@@ -334,11 +334,8 @@ nfs3svc_decode_readargs(struct svc_rqst *rqstp, __be32 *p,
 	if (!p)
 		return 0;
 	p = xdr_decode_hyper(p, &args->offset);
-	args->count = ntohl(*p++);
-
-	if (!xdr_argsize_check(rqstp, p))
-		return 0;
 
+	args->count = ntohl(*p++);
 	len = min(args->count, max_blocksize);
 
 	/* set up the kvec */
@@ -352,7 +349,7 @@ nfs3svc_decode_readargs(struct svc_rqst *rqstp, __be32 *p,
 		v++;
 	}
 	args->vlen = v;
-	return 1;
+	return xdr_argsize_check(rqstp, p);
 }
 
 int
@@ -544,11 +541,9 @@ nfs3svc_decode_readlinkargs(struct svc_rqst *rqstp, __be32 *p,
 	p = decode_fh(p, &args->fh);
 	if (!p)
 		return 0;
-	if (!xdr_argsize_check(rqstp, p))
-		return 0;
 	args->buffer = page_address(*(rqstp->rq_next_page++));
 
-	return 1;
+	return xdr_argsize_check(rqstp, p);
 }
 
 int
@@ -574,14 +569,10 @@ nfs3svc_decode_readdirargs(struct svc_rqst *rqstp, __be32 *p,
 	args->verf   = p; p += 2;
 	args->dircount = ~0;
 	args->count  = ntohl(*p++);
-
-	if (!xdr_argsize_check(rqstp, p))
-		return 0;
-
 	args->count  = min_t(u32, args->count, PAGE_SIZE);
 	args->buffer = page_address(*(rqstp->rq_next_page++));
 
-	return 1;
+	return xdr_argsize_check(rqstp, p);
 }
 
 int
@@ -599,9 +590,6 @@ nfs3svc_decode_readdirplusargs(struct svc_rqst *rqstp, __be32 *p,
 	args->dircount = ntohl(*p++);
 	args->count    = ntohl(*p++);
 
-	if (!xdr_argsize_check(rqstp, p))
-		return 0;
-
 	len = args->count = min(args->count, max_blocksize);
 	while (len > 0) {
 		struct page *p = *(rqstp->rq_next_page++);
@@ -609,7 +597,8 @@ nfs3svc_decode_readdirplusargs(struct svc_rqst *rqstp, __be32 *p,
 			args->buffer = page_address(p);
 		len -= PAGE_SIZE;
 	}
-	return 1;
+
+	return xdr_argsize_check(rqstp, p);
 }
 
 int

fs/nfsd/nfsxdr.c

@@ -257,9 +257,6 @@ nfssvc_decode_readargs(struct svc_rqst *rqstp, __be32 *p,
 	len = args->count     = ntohl(*p++);
 	p++; /* totalcount - unused */
 
-	if (!xdr_argsize_check(rqstp, p))
-		return 0;
-
 	len = min_t(unsigned int, len, NFSSVC_MAXBLKSIZE_V2);
 
 	/* set up somewhere to store response.
@@ -275,7 +272,7 @@ nfssvc_decode_readargs(struct svc_rqst *rqstp, __be32 *p,
 		v++;
 	}
 	args->vlen = v;
-	return 1;
+	return xdr_argsize_check(rqstp, p);
 }
 
 int
@@ -365,11 +362,9 @@ nfssvc_decode_readlinkargs(struct svc_rqst *rqstp, __be32 *p, struct nfsd_readli
 	p = decode_fh(p, &args->fh);
 	if (!p)
 		return 0;
-	if (!xdr_argsize_check(rqstp, p))
-		return 0;
 	args->buffer = page_address(*(rqstp->rq_next_page++));
 
-	return 1;
+	return xdr_argsize_check(rqstp, p);
 }
 
 int
@@ -407,11 +402,9 @@ nfssvc_decode_readdirargs(struct svc_rqst *rqstp, __be32 *p,
 	args->cookie = ntohl(*p++);
 	args->count  = ntohl(*p++);
 	args->count  = min_t(u32, args->count, PAGE_SIZE);
-	if (!xdr_argsize_check(rqstp, p))
-		return 0;
 	args->buffer = page_address(*(rqstp->rq_next_page++));
 
-	return 1;
+	return xdr_argsize_check(rqstp, p);
 }
 
 /*

include/linux/sunrpc/svc.h

@@ -336,7 +336,8 @@ xdr_argsize_check(struct svc_rqst *rqstp, __be32 *p)
 {
 	char *cp = (char *)p;
 	struct kvec *vec = &rqstp->rq_arg.head[0];
-	return cp == (char *)vec->iov_base + vec->iov_len;
+	return cp >= (char*)vec->iov_base
+		&& cp <= (char*)vec->iov_base + vec->iov_len;
 }
 
 static inline int