XArray: Fix xas_create_range for ranges above 4 billion

The 'sibs' variable would be shifted as a 32-bit integer, so if 'shift'
is more than 32, this is undefined behaviour.  In practice, this doesn't
happen because the page cache is the only user and nobody uses 16TB pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/lib/xarray.c b/lib/xarray.c
index 1fa5c56..2046d67 100644 (file)
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -703,7 +703,7 @@ void xas_create_range(struct xa_state *xas)
        unsigned char shift = xas->xa_shift;
        unsigned char sibs = xas->xa_sibs;
 
-       xas->xa_index |= ((sibs + 1) << shift) - 1;
+       xas->xa_index |= ((sibs + 1UL) << shift) - 1;
        if (xas_is_node(xas) && xas->xa_node->shift == xas->xa_shift)
                xas->xa_offset |= sibs;
        xas->xa_shift = 0;