From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fieldses.org ([173.255.197.46]:59644 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S977232AbdDXVUb (ORCPT ); Mon, 24 Apr 2017 17:20:31 -0400 Date: Mon, 24 Apr 2017 17:20:31 -0400 From: "J. Bruce Fields" To: NeilBrown Cc: linux-nfs@vger.kernel.org Subject: Re: [PATCH] nfsd: check for oversized NFSv2/v3 arguments Message-ID: <20170424212031.GB1585@fieldses.org> References: <20170414150440.GA5362@fieldses.org> <20170414150940.GB5362@fieldses.org> <87h91mtvdb.fsf@notabene.neil.brown.name> <20170418171351.GF6208@fieldses.org> <20170420161935.GB4782@fieldses.org> <20170421211253.GE19775@fieldses.org> <87vapurci7.fsf@notabene.neil.brown.name> <20170424140642.GB30046@fieldses.org> <20170424211920.GA1585@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: <20170424211920.GA1585@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: And, another problem spotted by the Synposys folks. I'll give these some more testing and hope to send a pull request in another day or two. --b. commit a0aa2db91590 Author: J. Bruce Fields Date: Fri Apr 21 15:26:30 2017 -0400 nfsd: stricter decoding of write-like NFSv2/v3 ops The NFSv2/v3 code does not systematically check whether we decode past the end of the buffer. This generally appears to be harmless, but there are a few places where we do arithmetic on the pointers involved and don't account for the possibility that a length could be negative. Add checks to catch these. Reported-by: Tuomas Haanpää Reported-by: Ari Kauppi Signed-off-by: J. Bruce Fields diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c index dba2ff8eaa68..41cc47bf9d00 100644 --- a/fs/nfsd/nfs3xdr.c +++ b/fs/nfsd/nfs3xdr.c @@ -358,6 +358,7 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, { unsigned int len, v, hdr, dlen; u32 max_blocksize = svc_max_payload(rqstp); + struct kvec *head = rqstp->rq_arg.head; p = decode_fh(p, &args->fh); if (!p) @@ -367,6 +368,8 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, args->count = ntohl(*p++); args->stable = ntohl(*p++); len = args->len = ntohl(*p++); + if ((void *)p > head->iov_base + head->iov_len) + return 0; /* * The count must equal the amount of data passed. */ @@ -466,11 +469,15 @@ nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p, len = ntohl(*p++); if (len == 0 || len > NFS3_MAXPATHLEN || len >= PAGE_SIZE) return 0; + if (!*(rqstp->rq_next_page)) + return 0; args->tname = new = page_address(*(rqstp->rq_next_page++)); args->tlen = len; /* first copy and check from the first page */ old = (char*)p; vec = &rqstp->rq_arg.head[0]; + if ((void *)old > vec->iov_base + vec->iov_len) + return 0; avail = vec->iov_len - (old - (char*)vec->iov_base); while (len && avail && *old) { *new++ = *old++; diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c index 41b468a6a90f..7a0eed7c619d 100644 --- a/fs/nfsd/nfsxdr.c +++ b/fs/nfsd/nfsxdr.c @@ -301,6 +301,8 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, * bytes. */ hdr = (void*)p - rqstp->rq_arg.head[0].iov_base; + if (hdr > rqstp->rq_arg.head[0].iov_len) + return 0; dlen = rqstp->rq_arg.head[0].iov_len + rqstp->rq_arg.page_len - hdr;