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>

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 452334694a5d1f37cc480e5d1cf2873c4246019d..12feac6ee2fd461a46c7b06b7a0ed0359fb4dfd1 100644 (file)
--- 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
@@ -541,9 +544,11 @@ 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
@@ -569,10 +574,14 @@ 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
@@ -590,6 +599,9 @@ 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++);
@@ -597,8 +609,7 @@ 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 de07ff625777820fefc98bfa56adea81962e8135..6a4947a3f4fa82be4118e4ed538a171118f4baa8 100644 (file)
--- 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
@@ -362,9 +365,11 @@ 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
@@ -402,9 +407,11 @@ 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 e770abeed32d7117c4f2d363f9d7370a60d2c55f..6ef19cf658b406bebfeb753584386e4d4789f6e5 100644 (file)
--- 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