[PATCH 4.9 161/164] nfsd: fix undefined behavior in nfsd4_layout_verify

[Greg Kroah-Hartman]

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

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

From: Ari Kauppi <ari@xxxxxxxxxxxx>

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@xxxxxxxxxxxx>
Signed-off-by: Ari Kauppi <ari@xxxxxxxxxxxx>
[colin.king@xxxxxxxxxxxxx: use LAYOUT_TYPE_MAX instead of 32]
Reviewed-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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;