nfsd: CVE-2017-7895

nfsd: stricter decoding of write-like NFSv2/v3 ops

References:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.1.y&id=5afff19d82af4e4ed66ce0320cd2f17053b78b25

Change-Id: Ibb3edd844b678bcb4c3dd115af77e77b0aa4eda9
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

2 files changed, 66 insertions, 0 deletions

diff --git a/patches/cve/4.1.x.scc b/patches/cve/4.1.x.scc
index 5722514..4741fca 100644
--- a/patches/cve/4.1.x.scc
+++ b/patches/cve/4.1.x.scc
@@ -6,3 +6,4 @@ patch CVE-2016-8655-packet-fix-race-condition-in-packet_set_ring.patch
 #fixed in 4.1.40
 patch CVE-2016-10229-udp-properly-support-MSG_PEEK-with-truncated-buffers.patch
 patch CVE-2017-7618-crypto-ahash-Fix-EINPROGRESS-notification-callback.patch
+patch CVE-2017-7895-nfsd-stricter-decoding-of-write-like-NFSv2-v3-ops.patch
diff --git a/patches/cve/CVE-2017-7895-nfsd-stricter-decoding-of-write-like-NFSv2-v3-ops.patch b/patches/cve/CVE-2017-7895-nfsd-stricter-decoding-of-write-like-NFSv2-v3-ops.patch
new file mode 100644
index 0000000..2ecf279
--- /dev/null
+++ b/patches/cve/CVE-2017-7895-nfsd-stricter-decoding-of-write-like-NFSv2-v3-ops.patch
@@ -0,0 +1,65 @@
+Date: Wed, 17 Oct 2018 10:55:24 +0200
+Subject: [PATCH] nfsd: stricter decoding of write-like NFSv2/v3 ops
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+[ Upstream commit 13bf9fbff0e5e099e2b6f003a0ab8ae145436309 ]
+
+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.
+
+CVE: CVE-2017-7895
+Upstream-Status: Backport
+
+Reported-by: Tuomas Haanpää <thaan@synopsys.com>
+Reported-by: Ari Kauppi <ari@synopsys.com>
+Reviewed-by: NeilBrown <neilb@suse.com>
+Cc: stable@vger.kernel.org
+Signed-off-by: J. Bruce Fields <bfields@redhat.com>
+Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ fs/nfsd/nfs3xdr.c | 4 ++++
+ fs/nfsd/nfsxdr.c | 2 ++
+ 2 file changed, 6 insertions(+)
+
+diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
+index 9cbcf53..ea21387 100644
+--- a/fs/nfsd/nfs3xdr.c
++++ b/fs/nfsd/nfs3xdr.c
+@@ -368,6 +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.
+         */
+@@ -471,6 +473,8 @@ 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 79d964a..74d3e76 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;
+ 
+--