diff options
| -rw-r--r-- | kernel/trace/trace_events_filter.c | 72 |
1 files changed, 71 insertions, 1 deletions
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 0a3e0502b507..91c9cdcb040b 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -1358,6 +1358,68 @@ static int count_preds(struct filter_parse_state *ps) return n_preds; } +/* + * The tree is walked at filtering of an event. If the tree is not correctly + * built, it may cause an infinite loop. Check here that the tree does + * indeed terminate. + */ +static int check_pred_tree(struct event_filter *filter, + struct filter_pred *root) +{ + struct filter_pred *preds; + struct filter_pred *pred; + enum move_type move = MOVE_DOWN; + int count = 0; + int done = 0; + int max; + + /* + * The max that we can hit a node is three times. + * Once going down, once coming up from left, and + * once coming up from right. This is more than enough + * since leafs are only hit a single time. + */ + max = 3 * filter->n_preds; + + preds = filter->preds; + if (!preds) + return -EINVAL; + pred = root; + + do { + if (WARN_ON(count++ > max)) + return -EINVAL; + + switch (move) { + case MOVE_DOWN: + if (pred->left != FILTER_PRED_INVALID) { + pred = &preds[pred->left]; + continue; + } + /* A leaf at the root is just a leaf in the tree */ + if (pred == root) + break; + pred = get_pred_parent(pred, preds, + pred->parent, &move); + continue; + case MOVE_UP_FROM_LEFT: + pred = &preds[pred->right]; + move = MOVE_DOWN; + continue; + case MOVE_UP_FROM_RIGHT: + if (pred == root) + break; + pred = get_pred_parent(pred, preds, + pred->parent, &move); + continue; + } + done = 1; + } while (!done); + + /* We are fine. */ + return 0; +} + static int replace_preds(struct ftrace_event_call *call, struct event_filter *filter, struct filter_parse_state *ps, @@ -1366,6 +1428,7 @@ static int replace_preds(struct ftrace_event_call *call, { char *operand1 = NULL, *operand2 = NULL; struct filter_pred *pred; + struct filter_pred *root; struct postfix_elt *elt; struct pred_stack stack = { }; /* init to NULL */ int err; @@ -1442,7 +1505,7 @@ add_pred: if (!pred) return -EINVAL; /* This item is where we start from in matching */ - filter->root = pred; + root = pred; /* Make sure the stack is empty */ pred = __pop_pred_stack(&stack); if (WARN_ON(pred)) { @@ -1450,6 +1513,13 @@ add_pred: filter->root = NULL; goto fail; } + err = check_pred_tree(filter, root); + if (err) + goto fail; + + /* We don't set root until we know it works */ + barrier(); + filter->root = root; } err = 0; |