[PATCH 5.10 048/406] kprobes: Prohibit probing on CFI preamble symbol

Greg Kroah-Hartman
2023-09-17T19:21:29Z

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

[ Upstream commit de02f2ac5d8cfb311f44f2bf144cc20002f1fbbd ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/kprobes.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 86d71c49b4957..f1ea3123f3832 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1628,6 +1628,17 @@ int __weak arch_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)
{
@@ -1646,7 +1657,8 @@ 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;
}
--
2.40.1