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Subject[PATCH 5.4 050/104] XArray: Fix infinite loop with entry at ULONG_MAX
Date
From: Matthew Wilcox (Oracle) <willy@infradead.org>

commit 430f24f94c8a174d411a550d7b5529301922e67a upstream.

If there is an entry at ULONG_MAX, xa_for_each() will overflow the
'index + 1' in xa_find_after() and wrap around to 0. Catch this case
and terminate the loop by returning NULL.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
lib/test_xarray.c | 17 +++++++++++++++++
lib/xarray.c | 3 +++
2 files changed, 20 insertions(+)

--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -1046,11 +1046,28 @@ static noinline void check_find_3(struct
xa_destroy(xa);
}

+static noinline void check_find_4(struct xarray *xa)
+{
+ unsigned long index = 0;
+ void *entry;
+
+ xa_store_index(xa, ULONG_MAX, GFP_KERNEL);
+
+ entry = xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT);
+ XA_BUG_ON(xa, entry != xa_mk_index(ULONG_MAX));
+
+ entry = xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT);
+ XA_BUG_ON(xa, entry);
+
+ xa_erase_index(xa, ULONG_MAX);
+}
+
static noinline void check_find(struct xarray *xa)
{
check_find_1(xa);
check_find_2(xa);
check_find_3(xa);
+ check_find_4(xa);
check_multi_find(xa);
check_multi_find_2(xa);
}
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1847,6 +1847,9 @@ void *xa_find_after(struct xarray *xa, u
XA_STATE(xas, xa, *indexp + 1);
void *entry;

+ if (xas.xa_index == 0)
+ return NULL;
+
rcu_read_lock();
for (;;) {
if ((__force unsigned int)filter < XA_MAX_MARKS)

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