[PATCH -tip] kprobes: Prohibit probing on BUG() and WARN() address

[Masami Hiramatsu]

Since BUG() and WARN() may use a trap (e.g. UD2 on x86) to
get the address where the BUG() has occurred, kprobes can not
do single-step out-of-line that instruction. So prohibit
probing on such address.

Without this fix, if someone put a kprobe on WARN(), the
kernel will crash with invalid opcode error instead of
outputing warning message, because kernel can not find
correct bug address.

Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
---
 kernel/kprobes.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 452151e79535..771054401e35 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1514,7 +1514,8 @@ static int check_kprobe_address_safe(struct kprobe *p,
        /* Ensure it is not in reserved area nor out of text */
        if (!kernel_text_address((unsigned long) p->addr) ||
            within_kprobe_blacklist((unsigned long) p->addr) ||
-           jump_label_text_reserved(p->addr, p->addr)) {
+           jump_label_text_reserved(p->addr, p->addr) ||
+           find_bug(p->addr)) {
                ret = -EINVAL;
                goto out;
        }