linux-kernel - [PATCH 4.4 102/103] nfsd: encoders mustnt use unitialized values in error cases

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Message-Id: <20170523200904.707517163@linuxfoundation.org>
Date:   Tue, 23 May 2017 22:10:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ari Kauppi <Ari.Kauppi@...opsys.com>,
        Christoph Hellwig <hch@....de>,
        "J. Bruce Fields" <bfields@...hat.com>
Subject: [PATCH 4.4 102/103] nfsd: encoders mustnt use unitialized values in error cases

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: J. Bruce Fields <bfields@...hat.com>

commit f961e3f2acae94b727380c0b74e2d3954d0edf79 upstream.

In error cases, lgp->lg_layout_type may be out of bounds; so we
shouldn't be using it until after the check of nfserr.

This was seen to crash nfsd threads when the server receives a LAYOUTGET
request with a large layout type.

GETDEVICEINFO has the same problem.

Reported-by: Ari Kauppi <Ari.Kauppi@...opsys.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfsd/nfs4xdr.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -4041,8 +4041,7 @@ nfsd4_encode_getdeviceinfo(struct nfsd4_
 		struct nfsd4_getdeviceinfo *gdev)
 {
 	struct xdr_stream *xdr = &resp->xdr;
-	const struct nfsd4_layout_ops *ops =
-		nfsd4_layout_ops[gdev->gd_layout_type];
+	const struct nfsd4_layout_ops *ops;
 	u32 starting_len = xdr->buf->len, needed_len;
 	__be32 *p;
 
@@ -4059,6 +4058,7 @@ nfsd4_encode_getdeviceinfo(struct nfsd4_
 
 	/* If maxcount is 0 then just update notifications */
 	if (gdev->gd_maxcount != 0) {
+		ops = nfsd4_layout_ops[gdev->gd_layout_type];
 		nfserr = ops->encode_getdeviceinfo(xdr, gdev);
 		if (nfserr) {
 			/*
@@ -4111,8 +4111,7 @@ nfsd4_encode_layoutget(struct nfsd4_comp
 		struct nfsd4_layoutget *lgp)
 {
 	struct xdr_stream *xdr = &resp->xdr;
-	const struct nfsd4_layout_ops *ops =
-		nfsd4_layout_ops[lgp->lg_layout_type];
+	const struct nfsd4_layout_ops *ops;
 	__be32 *p;
 
 	dprintk("%s: err %d\n", __func__, nfserr);
@@ -4135,6 +4134,7 @@ nfsd4_encode_layoutget(struct nfsd4_comp
 	*p++ = cpu_to_be32(lgp->lg_seg.iomode);
 	*p++ = cpu_to_be32(lgp->lg_layout_type);
 
+	ops = nfsd4_layout_ops[lgp->lg_layout_type];
 	nfserr = ops->encode_layoutget(xdr, lgp);
 out:
 	kfree(lgp->lg_content);