kprobes: Fix possible use-after-free issue on kprobe registration

When unloading a module, its state is changing MODULE_STATE_LIVE -> MODULE_STATE_GOING -> MODULE_STATE_UNFORMED. Each change will take a time. `is_module_text_address()` and `__module_text_address()` works with MODULE_STATE_LIVE and MODULE_STATE_GOING. If we use `is_module_text_address()` and `__module_text_address()` separately, there is a chance that the first one is succeeded but the next one is failed because module->state becomes MODULE_STATE_UNFORMED between those operations. In `check_kprobe_address_safe()`, if the second `__module_text_address()` is failed, that is ignored because it expected a kernel_text address. But it may have failed simply because module->state has been changed to MODULE_STATE_UNFORMED. In this case, arm_kprobe() will try to modify non-exist module text address (use-after-free). To fix this problem, we should not use separated `is_module_text_address()` and `__module_text_address()`, but use only `__module_text_address()` once and do `try_module_get(module)` which is only available with MODULE_STATE_LIVE. Link: https://lore.kernel.org/all/[email protected]/ Fixes: 28f6c37 ("kprobes: Forbid probing on trampoline and BPF code areas") Cc: [email protected] Signed-off-by: Zheng Yejian <[email protected]> Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
torvalds · Apr 10, 2024 · 325f3fb · 325f3fb
1 parent fec50db
commit 325f3fb
Showing 1 changed file with 12 additions and 6 deletions.
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
@@ -1567,10 +1567,17 @@ static int check_kprobe_address_safe(struct kprobe *p,
  jump_label_lock();
  preempt_disable();
 
- /* Ensure it is not in reserved area nor out of text */
- if (!(core_kernel_text((unsigned long) p->addr) ||
- is_module_text_address((unsigned long) p->addr)) ||
- in_gate_area_no_mm((unsigned long) p->addr) ||
+ /* Ensure the address is in a text area, and find a module if exists. */
+ *probed_mod = NULL;
+ if (!core_kernel_text((unsigned long) p->addr)) {
+ *probed_mod = __module_text_address((unsigned long) p->addr);
+ if (!(*probed_mod)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ }
+ /* Ensure it is not in reserved area. */
+ if (in_gate_area_no_mm((unsigned long) p->addr) ||
  within_kprobe_blacklist((unsigned long) p->addr) ||
  jump_label_text_reserved(p->addr, p->addr) ||
  static_call_text_reserved(p->addr, p->addr) ||
@@ -1580,8 +1587,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
  goto out;
  }
 
- /* Check if 'p' is probing a module. */
- *probed_mod = __module_text_address((unsigned long) p->addr);
+ /* Get module refcount and reject __init functions for loaded modules. */
  if (*probed_mod) {
  /*
  * We must hold a refcount of the probed module while updating