linux-kernel - [PATCH 4.9 161/164] nfsd: fix undefined behavior in nfsd4_layout

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Date:   Tue, 23 May 2017 22:09:38 +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, Jani Tuovila <tuovila@...opsys.com>,
        Ari Kauppi <ari@...opsys.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Christoph Hellwig <hch@....de>,
        "J. Bruce Fields" <bfields@...hat.com>
Subject: [PATCH 4.9 161/164] nfsd: fix undefined behavior in nfsd4_layout_verify

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

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

From: Ari Kauppi <ari@...opsys.com>

commit b550a32e60a4941994b437a8d662432a486235a5 upstream.

  UBSAN: Undefined behaviour in fs/nfsd/nfs4proc.c:1262:34
  shift exponent 128 is too large for 32-bit type 'int'

Depending on compiler+architecture, this may cause the check for
layout_type to succeed for overly large values (which seems to be the
case with amd64). The large value will be later used in de-referencing
nfsd4_layout_ops for function pointers.

Reported-by: Jani Tuovila <tuovila@...opsys.com>
Signed-off-by: Ari Kauppi <ari@...opsys.com>
[colin.king@...onical.com: use LAYOUT_TYPE_MAX instead of 32]
Reviewed-by: Dan Carpenter <dan.carpenter@...cle.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/nfs4proc.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1273,7 +1273,8 @@ nfsd4_layout_verify(struct svc_export *e
 		return NULL;
 	}

-	if (!(exp->ex_layout_types & (1 << layout_type))) {
+	if (layout_type >= LAYOUT_TYPE_MAX ||
+	    !(exp->ex_layout_types & (1 << layout_type))) {
 		dprintk("%s: layout type %d not supported\n",
 			__func__, layout_type);
 		return NULL;