Patch "nfsd: check for oversized NFSv2/v3 arguments" has been added to the 4.4-stable tree

From 51f567777799c9d85a778302b9eb61cf15214a98 Mon Sep 17 00:00:00 2001

This is a note to let you know that I've just added the patch titled

nfsd: check for oversized NFSv2/v3 arguments

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nfsd-check-for-oversized-nfsv2-v3-arguments.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From 51f567777799c9d85a778302b9eb61cf15214a98 Mon Sep 17 00:00:00 2001
From: "J. Bruce Fields" <[email protected]>
Date: Thu, 6 Apr 2017 22:36:31 -0400
Subject: nfsd: check for oversized NFSv2/v3 arguments
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From: J. Bruce Fields <[email protected]>

commit 51f567777799c9d85a778302b9eb61cf15214a98 upstream.

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 Haanp�� <[email protected]>

Reported-by Ari Kauppi <[email protected]>

Signed-off-by J. Bruce Fields <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 fs/nfsd/nfs3xdr.c          |   23 +++++++++++++++++------
 fs/nfsd/nfsxdr.c           |   13 ++++++++++---
 include/linux/sunrpc/svc.h |    3 +--
 3 files changed, 28 insertions(+), 11 deletions(-)

fs/nfsd/nfs3xdr.c +17 -6

@@ -334,8 +334,11 @@ nfs3svc_decode_readargs(struct svc_rqst
 	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
 		v++;
 	}
 	args->vlen = v;
-	return xdr_argsize_check(rqstp, p);
+	return 1;
 }
 
 int

@@ -540,9 +543,11 @@ nfs3svc_decode_readlinkargs(struct svc_r
 	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

@@ -568,10 +573,14 @@ nfs3svc_decode_readdirargs(struct svc_rq
 	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

@@ -589,6 +598,9 @@ nfs3svc_decode_readdirplusargs(struct sv
 	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++);

@@ -596,8 +608,7 @@ nfs3svc_decode_readdirplusargs(struct sv
 			args->buffer = page_address(p);
 		len -= PAGE_SIZE;
 	}
-
-	return xdr_argsize_check(rqstp, p);
+	return 1;
 }
 
 int

fs/nfsd/nfsxdr.c +10 -3

@@ -257,6 +257,9 @@ nfssvc_decode_readargs(struct svc_rqst *
 	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 *
 		v++;
 	}
 	args->vlen = v;
-	return xdr_argsize_check(rqstp, p);
+	return 1;
 }
 
 int

@@ -362,9 +365,11 @@ nfssvc_decode_readlinkargs(struct svc_rq
 	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

@@ -402,9 +407,11 @@ nfssvc_decode_readdirargs(struct svc_rqs
 	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;
 }
 
 /*

include/linux/sunrpc/svc.h +1 -2

@@ -335,8 +335,7 @@ xdr_argsize_check(struct svc_rqst *rqstp
 {
 	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

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/nfsd-check-for-oversized-nfsv2-v3-arguments.patch queue-4.4/nfsd-encoders-mustn-t-use-unitialized-values-in-error-cases.patch queue-4.4/nfsd-fix-up-the-supattr_exclcreat-attributes.patch