Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues: - [Critical] Race condition in unregister_trace_uprobe leads to use-after-free (UAF) of trace_uprobe during lockless read accesses. -- commit 04fcafa318e6d04f74e677950139db1dd3bf079c Author: Zafir Rasyidi Taufik <[email protected]> tracing: uprobes: Fix slab use-after-free in filter_chain This commit addresses a use-after-free in uprobe_mmap. It resolves an issue where unregister_trace_uprobe() would fail to unlink the consumer when a trace_probe has a sibling event. > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c > index 861d857adadb3..110ec7b78b3dc 100644 > --- a/kernel/trace/trace_uprobe.c > +++ b/kernel/trace/trace_uprobe.c > @@ -408,6 +408,11 @@ static int unregister_trace_uprobe(struct trace_uprobe > *tu) > return ret; > > unreg: > + if (tu->uprobe) { > + uprobe_unregister_nosync(tu->uprobe, &tu->consumer); > + tu->uprobe = NULL; > + uprobe_unregister_sync(); > + } > dyn_event_remove(&tu->devent); > trace_probe_unlink(&tu->tp); > free_trace_uprobe(tu); [Severity: Critical] This is a pre-existing issue, but does this code leave a window for a use-after-free of trace_uprobe during lockless read accesses? When a sibling probe exists, this code unlinks and immediately frees the trace probe without synchronizing with trace readers via RCU or shared locks. For example, when a user queries an attached perf event, it initiates a lockless traversal: bpf_task_fd_query() bpf_get_perf_event_info() bpf_get_uprobe_info() trace_uprobe_primary_from_call() This accesses the trace probe structure without acquiring event_mutex or trace_event_sem. Additionally, even if trace_event_sem is held for read, such as during print_uprobe_event(), unregister_trace_uprobe() bypasses taking trace_event_sem for write when unregistering a sibling probe (it skips unregister_uprobe_event() and jumps directly to unreg). At the same time, if unregister_trace_uprobe() is called, it unlinks the probe via trace_probe_unlink(). The list removal relies on standard list_del_init() instead of list_del_rcu(), allowing concurrent lockless readers to traverse into soon-to-be-freed nodes when free_trace_uprobe(tu) is called immediately after. Could this lead to memory corruption when readers access the freed probe? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
