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-rw-r--r--kernel/bpf/syscall.c30
1 files changed, 18 insertions, 12 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5d141f16f6fa..272071e9112f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1707,20 +1707,26 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
if (err)
goto free_used_maps;
- err = bpf_prog_new_fd(prog);
- if (err < 0) {
- /* failed to allocate fd.
- * bpf_prog_put() is needed because the above
- * bpf_prog_alloc_id() has published the prog
- * to the userspace and the userspace may
- * have refcnt-ed it through BPF_PROG_GET_FD_BY_ID.
- */
- bpf_prog_put(prog);
- return err;
- }
-
+ /* Upon success of bpf_prog_alloc_id(), the BPF prog is
+ * effectively publicly exposed. However, retrieving via
+ * bpf_prog_get_fd_by_id() will take another reference,
+ * therefore it cannot be gone underneath us.
+ *
+ * Only for the time /after/ successful bpf_prog_new_fd()
+ * and before returning to userspace, we might just hold
+ * one reference and any parallel close on that fd could
+ * rip everything out. Hence, below notifications must
+ * happen before bpf_prog_new_fd().
+ *
+ * Also, any failure handling from this point onwards must
+ * be using bpf_prog_put() given the program is exposed.
+ */
bpf_prog_kallsyms_add(prog);
perf_event_bpf_event(prog, PERF_BPF_EVENT_PROG_LOAD, 0);
+
+ err = bpf_prog_new_fd(prog);
+ if (err < 0)
+ bpf_prog_put(prog);
return err;
free_used_maps: