From f34b95689d2ce001c157b1604289ff240b4bdee0 Mon Sep 17 00:00:00 2001 From: Peter Staubach Date: Wed, 9 May 2007 02:34:48 -0700 Subject: The NFSv2/NFSv3 server does not handle zero length WRITE requests correctly The NFSv2 and NFSv3 servers do not handle WRITE requests for 0 bytes correctly. The specifications indicate that the server should accept the request, but it should mostly turn into a no-op. Currently, the server will return an XDR decode error, which it should not. Attached is a patch which addresses this issue. It also adds some boundary checking to ensure that the request contains as much data as was requested to be written. It also correctly handles an NFSv3 request which requests to write more data than the server has stated that it is prepared to handle. Previously, there was some support which looked like it should work, but wasn't quite right. Signed-off-by: Peter Staubach Acked-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/nfsd/nfsxdr.c | 46 +++++++++++++++++++++++++++++++++++++++------- 1 file changed, 39 insertions(+), 7 deletions(-) (limited to 'fs/nfsd/nfsxdr.c') diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c index 0c24b9e24fe8..6035e03655c6 100644 --- a/fs/nfsd/nfsxdr.c +++ b/fs/nfsd/nfsxdr.c @@ -284,8 +284,9 @@ int nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, struct nfsd_writeargs *args) { - unsigned int len; + unsigned int len, hdr, dlen; int v; + if (!(p = decode_fh(p, &args->fh))) return 0; @@ -293,11 +294,42 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, args->offset = ntohl(*p++); /* offset */ p++; /* totalcount */ len = args->len = ntohl(*p++); - rqstp->rq_vec[0].iov_base = (void*)p; - rqstp->rq_vec[0].iov_len = rqstp->rq_arg.head[0].iov_len - - (((void*)p) - rqstp->rq_arg.head[0].iov_base); + /* + * The protocol specifies a maximum of 8192 bytes. + */ if (len > NFSSVC_MAXBLKSIZE_V2) - len = NFSSVC_MAXBLKSIZE_V2; + return 0; + + /* + * Check to make sure that we got the right number of + * bytes. + * + * If more than one page was used, then compute the length + * of the data in the request as the total size of the + * request minus the transport protocol headers minus the + * RPC protocol headers minus the NFS protocol fields + * already consumed. If the request fits into a single + * page, then compete the length of the data as the size + * of the NFS portion of the request minus the NFS + * protocol fields already consumed. + */ + hdr = (void*)p - rqstp->rq_arg.head[0].iov_base; + if (rqstp->rq_respages != rqstp->rq_pages + 1) { + dlen = rqstp->rq_arg.len - + (PAGE_SIZE - rqstp->rq_arg.head[0].iov_len) - hdr; + } else { + dlen = rqstp->rq_arg.head[0].iov_len - hdr; + } + /* + * Round the length of the data which was specified up to + * the next multiple of XDR units and then compare that + * against the length which was actually received. + */ + if (dlen != ((len + 3) & ~0x3)) + return 0; + + rqstp->rq_vec[0].iov_base = (void*)p; + rqstp->rq_vec[0].iov_len = rqstp->rq_arg.head[0].iov_len - hdr; v = 0; while (len > rqstp->rq_vec[v].iov_len) { len -= rqstp->rq_vec[v].iov_len; @@ -306,8 +338,8 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, rqstp->rq_vec[v].iov_len = PAGE_SIZE; } rqstp->rq_vec[v].iov_len = len; - args->vlen = v+1; - return rqstp->rq_vec[0].iov_len > 0; + args->vlen = v + 1; + return 1; } int -- cgit v1.2.2