From 51f567777799c9d85a778302b9eb61cf15214a98 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Thu, 6 Apr 2017 22:36:31 -0400 Subject: [PATCH] nfsd: check for oversized NFSv2/v3 arguments MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Reported-by: Ari Kauppi Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields --- 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 452334694a5d..12feac6ee2fd 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 @@ -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 de07ff625777..6a4947a3f4fa 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 @@ -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 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 -- 2.20.1