From c36d451ad386b34f452fc3c8621ff14b9eaa31a6 Mon Sep 17 00:00:00 2001
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: Fri, 31 Jan 2020 06:17:09 -0500
Subject: [PATCH] XArray: Fix xas_pause for large multi-index entries

Inspired by the recent Coverity report, I looked for other places where
the offset wasn't being converted to an unsigned long before being
shifted, and I found one in xas_pause() when the entry being paused is
of order >32.

Fixes: b803b42823d0 ("xarray: Add XArray iterators")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: stable@vger.kernel.org
---
 lib/test_xarray.c | 37 +++++++++++++++++++++++++++++++++++++
 lib/xarray.c      |  2 +-
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index 8c7d7a8468b8..d4f97925dbd8 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -1156,6 +1156,42 @@ static noinline void check_find_entry(struct xarray *xa)
 	XA_BUG_ON(xa, !xa_empty(xa));
 }
 
+static noinline void check_pause(struct xarray *xa)
+{
+	XA_STATE(xas, xa, 0);
+	void *entry;
+	unsigned int order;
+	unsigned long index = 1;
+	unsigned int count = 0;
+
+	for (order = 0; order < order_limit; order++) {
+		XA_BUG_ON(xa, xa_store_order(xa, index, order,
+					xa_mk_index(index), GFP_KERNEL));
+		index += 1UL << order;
+	}
+
+	rcu_read_lock();
+	xas_for_each(&xas, entry, ULONG_MAX) {
+		XA_BUG_ON(xa, entry != xa_mk_index(1UL << count));
+		count++;
+	}
+	rcu_read_unlock();
+	XA_BUG_ON(xa, count != order_limit);
+
+	count = 0;
+	xas_set(&xas, 0);
+	rcu_read_lock();
+	xas_for_each(&xas, entry, ULONG_MAX) {
+		XA_BUG_ON(xa, entry != xa_mk_index(1UL << count));
+		count++;
+		xas_pause(&xas);
+	}
+	rcu_read_unlock();
+	XA_BUG_ON(xa, count != order_limit);
+
+	xa_destroy(xa);
+}
+
 static noinline void check_move_tiny(struct xarray *xa)
 {
 	XA_STATE(xas, xa, 0);
@@ -1664,6 +1700,7 @@ static int xarray_checks(void)
 	check_xa_alloc();
 	check_find(&array);
 	check_find_entry(&array);
+	check_pause(&array);
 	check_account(&array);
 	check_destroy(&array);
 	check_move(&array);
diff --git a/lib/xarray.c b/lib/xarray.c
index acd1fad2e862..05324cf571f4 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -970,7 +970,7 @@ void xas_pause(struct xa_state *xas)
 
 	xas->xa_node = XAS_RESTART;
 	if (node) {
-		unsigned int offset = xas->xa_offset;
+		unsigned long offset = xas->xa_offset;
 		while (++offset < XA_CHUNK_SIZE) {
 			if (!xa_is_sibling(xa_entry(xas->xa, node, offset)))
 				break;