maple_tree: reduce user error potential

When iterating, a user may operate on the tree and cause the maple state
to be altered and left in an unintuitive state.  Detect this scenario and
correct it by setting to the limit and invalidating the state.

Link: https://lkml.kernel.org/r/20230120162650.984577-4-Liam.Howlett@oracle.com
Cc: <Stable@vger.kernel.org>
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 1ade7748cc9b7d9dc0077b21851a95a7e22de2fc..819ba692940e49b59ba02e58680a04af3a717887 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4737,6 +4737,11 @@ static inline void *mas_next_entry(struct ma_state *mas, unsigned long limit)
        unsigned long last;
        enum maple_type mt;
 
+       if (mas->index > limit) {
+               mas->index = mas->last = limit;
+               mas_pause(mas);
+               return NULL;
+       }
        last = mas->last;
 retry:
        offset = mas->offset;
@@ -4843,6 +4848,11 @@ static inline void *mas_prev_entry(struct ma_state *mas, unsigned long min)
 {
        void *entry;
 
+       if (mas->index < min) {
+               mas->index = mas->last = min;
+               mas_pause(mas);
+               return NULL;
+       }
 retry:
        while (likely(!mas_is_none(mas))) {
                entry = mas_prev_nentry(mas, min, mas->index);