From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fieldses.org ([173.255.197.46]:33026 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1949789AbdDYUkR (ORCPT ); Tue, 25 Apr 2017 16:40:17 -0400 Date: Tue, 25 Apr 2017 16:40:16 -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: <20170425204016.GA15279@fieldses.org> References: <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> <20170424212031.GB1585@fieldses.org> <87o9vlp48j.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: <87o9vlp48j.fsf@notabene.neil.brown.name> Sender: linux-nfs-owner@vger.kernel.org List-ID: > > + if (!*(rqstp->rq_next_page)) > > + return 0; > > Why the extra parentheses? "->" is at the highest precedence level for C. I've been doing this stuff enough years, you'd think I'd have bothered to memorize the C operator precedence table by now. Anyway, this change is actually unrelated and not entirely necessary; dropped. > i.e. either keep it simple (like the v2 code) or make it tidy (with head > and tail), but not half-and-half?? What the heck, let's go all out. You only live once! --b. commit db44bac41bbf Author: J. Bruce Fields Date: Tue Apr 25 16:21:34 2017 -0400 nfsd4: minor NFSv2/v3 write decoding cleanup Use a couple shortcuts that will simplify a following bugfix. Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c index dba2ff8eaa68..d18cfddbe115 100644 --- a/fs/nfsd/nfs3xdr.c +++ b/fs/nfsd/nfs3xdr.c @@ -358,6 +358,8 @@ 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; + struct kvec *tail = rqstp->rq_arg.tail; p = decode_fh(p, &args->fh); if (!p) @@ -377,9 +379,8 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, * Check to make sure that we got the right number of * bytes. */ - hdr = (void*)p - rqstp->rq_arg.head[0].iov_base; - dlen = rqstp->rq_arg.head[0].iov_len + rqstp->rq_arg.page_len - + rqstp->rq_arg.tail[0].iov_len - hdr; + hdr = (void*)p - head->iov_base; + dlen = head->iov_len + rqstp->rq_arg.page_len + tail->iov_len - hdr; /* * Round the length of the data which was specified up to * the next multiple of XDR units and then compare that @@ -396,7 +397,7 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, len = args->len = max_blocksize; } rqstp->rq_vec[0].iov_base = (void*)p; - rqstp->rq_vec[0].iov_len = rqstp->rq_arg.head[0].iov_len - hdr; + rqstp->rq_vec[0].iov_len = head->iov_len - hdr; v = 0; while (len > rqstp->rq_vec[v].iov_len) { len -= rqstp->rq_vec[v].iov_len; diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c index 41b468a6a90f..59bd88a23a3d 100644 --- a/fs/nfsd/nfsxdr.c +++ b/fs/nfsd/nfsxdr.c @@ -280,6 +280,7 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, struct nfsd_writeargs *args) { unsigned int len, hdr, dlen; + struct kvec *head = rqstp->rq_arg.head; int v; p = decode_fh(p, &args->fh); @@ -300,9 +301,8 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, * Check to make sure that we got the right number of * bytes. */ - hdr = (void*)p - rqstp->rq_arg.head[0].iov_base; - dlen = rqstp->rq_arg.head[0].iov_len + rqstp->rq_arg.page_len - - hdr; + hdr = (void*)p - head->iov_base; + dlen = head->iov_len + rqstp->rq_arg.page_len - hdr; /* * Round the length of the data which was specified up to @@ -316,7 +316,7 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, return 0; rqstp->rq_vec[0].iov_base = (void*)p; - rqstp->rq_vec[0].iov_len = rqstp->rq_arg.head[0].iov_len - hdr; + rqstp->rq_vec[0].iov_len = head->iov_len - hdr; v = 0; while (len > rqstp->rq_vec[v].iov_len) { len -= rqstp->rq_vec[v].iov_len; commit 13bf9fbff0e5 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 Reviewed-by: NeilBrown Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c index d18cfddbe115..452334694a5d 100644 --- a/fs/nfsd/nfs3xdr.c +++ b/fs/nfsd/nfs3xdr.c @@ -369,6 +369,8 @@ 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. */ @@ -472,6 +474,8 @@ nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p, /* 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 59bd88a23a3d..de07ff625777 100644 --- a/fs/nfsd/nfsxdr.c +++ b/fs/nfsd/nfsxdr.c @@ -302,6 +302,8 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p, * bytes. */ hdr = (void*)p - head->iov_base; + if (hdr > head->iov_len) + return 0; dlen = head->iov_len + rqstp->rq_arg.page_len - hdr; /*