diff mbox

nfsd: check for oversized NFSv2/v3 arguments

Message ID 20170414150440.GA5362@fieldses.org (mailing list archive)
State New, archived
Headers show

Commit Message

J. Bruce Fields April 14, 2017, 3:04 p.m. UTC 
From: "J. Bruce Fields" <bfields@redhat.com>

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(-)

Comments

J. Bruce Fields April 14, 2017, 3:09 p.m. UTC | #1 
(Cc'd you, Neil, partly on the off chance you might have a better idea
where this came from.  Looks to me like it may have been there forever,
but, I haven't looked too hard yet.)

--b.

On Fri, Apr 14, 2017 at 11:04:40AM -0400, bfields wrote:
> From: "J. Bruce Fields" <bfields@redhat.com>
> 
> 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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diff mbox

Patch

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