kprobes: Prohibit probing on CFI preamble symbol

Do not allow to probe on "__cfi_" or "__pfx_" started symbol, because those
are used for CFI and not executed. Probing it will break the CFI.

Link: https://lore.kernel.org/all/168904024679.116016.18089228029322008512.stgit@devnote2/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1fc6095d502d9c83c1317d90057a907df91d5be6..ca385b61d546722161f3c720fdf3198f4e9445d1 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1545,6 +1545,17 @@ static int check_ftrace_location(struct kprobe *p)
        return 0;
 }
 
+static bool is_cfi_preamble_symbol(unsigned long addr)
+{
+       char symbuf[KSYM_NAME_LEN];
+
+       if (lookup_symbol_name(addr, symbuf))
+               return false;
+
+       return str_has_prefix("__cfi_", symbuf) ||
+               str_has_prefix("__pfx_", symbuf);
+}
+
 static int check_kprobe_address_safe(struct kprobe *p,
                                     struct module **probed_mod)
 {
@@ -1563,7 +1574,8 @@ static int check_kprobe_address_safe(struct kprobe *p,
            within_kprobe_blacklist((unsigned long) p->addr) ||
            jump_label_text_reserved(p->addr, p->addr) ||
            static_call_text_reserved(p->addr, p->addr) ||
-           find_bug((unsigned long)p->addr)) {
+           find_bug((unsigned long)p->addr) ||
+           is_cfi_preamble_symbol((unsigned long)p->addr)) {
                ret = -EINVAL;
                goto out;
        }