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/20240410015802.265220-1-zhengyejian1@huawei.com/

Fixes: 28f6c37a2910 ("kprobes: Forbid probing on trampoline and BPF code areas")
Cc: stable@vger.kernel.org
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

1 files changed, 12 insertions, 6 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 9d9095e81792..65adc815fc6e 100644
--- 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