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nfsd: fix undefined behavior in nfsd4_layout_verify

  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 <>
Signed-off-by: Ari Kauppi <>
[ use LAYOUT_TYPE_MAX instead of 32]
Reviewed-by: Dan Carpenter <>
Reviewed-by: Christoph Hellwig <>
Signed-off-by: J. Bruce Fields <>
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Ari Kauppi J. Bruce Fields
Ari Kauppi authored and J. Bruce Fields committed May 5, 2017
1 parent efda760 commit b550a32e60a4941994b437a8d662432a486235a5
Showing with 2 additions and 1 deletion.
  1. +2 −1 fs/nfsd/nfs4proc.c
@@ -1259,7 +1259,8 @@ nfsd4_layout_verify(struct svc_export *exp, unsigned int layout_type)
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;

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