From: "J. Bruce Fields" <bfields@redhat.com>

Date:       2017-04-14 15:04:40

Subject:    [PATCH] nfsd: check for oversized NFSv2/v3 arguments

A client can append random data to the end of an NFSv2 or NFSv3 RPC call

without our complaining; we'll just stop parsing at the end of the

expected data and ignore the rest.

Encoded arguments and replies are stored together in an array of pages,

and if a call is too large it could leave inadequate space for the

reply.  This is normally OK because NFS RPC's typically have either

short arguments and long replies (like READ) or long arguments and short

replies (like WRITE).  But a client that sends an incorrectly long reply

can violate those assumptions.  This was observed to cause crashes.

So, insist that the argument not be any longer than we expect.

Also, several operations increment rq_next_page in the decode routine

before checking the argument size, which can leave rq_next_page pointing

well past the end of the page array, causing trouble later in

svc_free_pages.

As followup we may also want to rewrite the encoding routines to check

more carefully that they aren't running off the end of the page array.

Reported-by: Tuomas Haanpää <thaan@synopsys.com>

Reported-by: Ari Kauppi <ari@synopsys.com>

Cc: stable@vger.kernel.org

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

---

 fs/nfsd/nfs3xdr.c          | 23 +++++++++++++++++------

 fs/nfsd/nfsxdr.c           | 13 ++++++++++---

 include/linux/sunrpc/svc.h |  3 +--

 3 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c

index dba2ff8eaa68..be66bcadfaea 100644

--- a/fs/nfsd/nfs3xdr.c

+++ b/fs/nfsd/nfs3xdr.c

@@ -334,8 +334,11 @@ 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;

+

 	len = min(args->count, max_blocksize);

 	/* set up the kvec */

@@ -349,7 +352,7 @@ nfs3svc_decode_readargs(struct svc_rqst *rqstp, __be32 *p,

 		v++;

 	}

 	args->vlen = v;

-	return xdr_argsize_check(rqstp, p);

+	return 1;

 }

 int

@@ -536,9 +539,11 @@ 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 xdr_argsize_check(rqstp, p);

+	return 1;

 }

 int

@@ -564,10 +569,14 @@ 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 xdr_argsize_check(rqstp, p);

+	return 1;

 }

 int

@@ -585,6 +594,9 @@ 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++);

@@ -592,8 +604,7 @@ nfs3svc_decode_readdirplusargs(struct svc_rqst *rqstp, __be32 *p,

 			args->buffer = page_address(p);

 		len -= PAGE_SIZE;

 	}

-

-	return xdr_argsize_check(rqstp, p);

+	return 1;

 }

 int

diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c

index 41b468a6a90f..79268369f7b3 100644

--- a/fs/nfsd/nfsxdr.c

+++ b/fs/nfsd/nfsxdr.c

@@ -257,6 +257,9 @@ 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.

@@ -272,7 +275,7 @@ nfssvc_decode_readargs(struct svc_rqst *rqstp, __be32 *p,

 		v++;

 	}

 	args->vlen = v;

-	return xdr_argsize_check(rqstp, p);

+	return 1;

 }

 int

@@ -360,9 +363,11 @@ 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 xdr_argsize_check(rqstp, p);

+	return 1;

 }

 int

@@ -400,9 +405,11 @@ 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 xdr_argsize_check(rqstp, p);

+	return 1;

 }

 /*

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h

index e770abeed32d..6ef19cf658b4 100644

--- a/include/linux/sunrpc/svc.h

+++ b/include/linux/sunrpc/svc.h

@@ -336,8 +336,7 @@ 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

-		&& cp <= (char*)vec->iov_base + vec->iov_len;

+	return cp == (char *)vec->iov_base + vec->iov_len;

 }

 static inline int

-- 

2.9.3

--

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