[PATCH v3] kprobes: Forbid probing on trampoline and bpf prog

Chen Zhongjin
2022-08-01T03:40:19Z

kernel_text_address returns ftrace_trampoline, kprobe_insn_slot
and bpf_text_address as kprobe legal address.

These text are removable and changeable without any notifier to
kprobes. Probing on them can trigger some unexpected behavior[1].

Considering that jump_label and static_call text are already be
forbiden to probe, kernel_text_address should be replaced with
core_kernel_text and is_module_text_address to check other text
which is unsafe to kprobe.

[1] https://lkml.org/lkml/2022/7/26/1148

Fixes: 5b485629ba0d ("kprobes, extable: Identify kprobes trampolines as kernel text area")
Fixes: 74451e66d516 ("bpf: make jited programs visible in traces")
Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
---
v2 -> v3:
Remove '-next' carelessly added in title.

v1 -> v2:
Check core_kernel_text and is_module_text_address rather than
only kprobe_insn.
Also fix title and commit message for this. See old patch at [1].
---
kernel/kprobes.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f214f8c088ed..80697e5e03e4 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1560,7 +1560,8 @@ static int check_kprobe_address_safe(struct kprobe *p,
preempt_disable();

/* Ensure it is not in reserved area nor out of text */
- if (!kernel_text_address((unsigned long) p->addr) ||
+ if (!(core_kernel_text((unsigned long) p->addr) ||
+ is_module_text_address((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) ||
--
2.17.1