nfsd: fix buffer overrun decoding NFSv4 acl

The array we kmalloc() here is not large enough.

Thanks to Johann Dahm and David Richter for bug report and testing.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: David Richter <richterd@citi.umich.edu>
Tested-by: Johann Dahm <jdahm@umich.edu>

fs/nfsd/nfs4acl.c

@@ -443,7 +443,7 @@ init_state(struct posix_acl_state *state, int cnt)
 	 * enough space for either:
 	 */
 	alloc = sizeof(struct posix_ace_state_array)
-		+ cnt*sizeof(struct posix_ace_state);
+		+ cnt*sizeof(struct posix_user_ace_state);
 	state->users = kzalloc(alloc, GFP_KERNEL);
 	if (!state->users)
 		return -ENOMEM;