[PATCH] kprobes: Warn if the kprobe is reregistered

From: Masami Hiramatsu
Date: Wed Feb 03 2021 - 10:00:30 EST


Warn if the kprobe is reregistered, since there must be
a software bug (actively used resource must not be re-registered)
and caller must be fixed.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
kernel/kprobes.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d5a3eb74a657..dd1d027455c4 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1520,13 +1520,16 @@ static struct kprobe *__get_valid_kprobe(struct kprobe *p)
return ap;
}

-/* Return error if the kprobe is being re-registered */
-static inline int check_kprobe_rereg(struct kprobe *p)
+/*
+ * Warn and return error if the kprobe is being re-registered since
+ * there must be a software bug.
+ */
+static inline int warn_kprobe_rereg(struct kprobe *p)
{
int ret = 0;

mutex_lock(&kprobe_mutex);
- if (__get_valid_kprobe(p))
+ if (WARN_ON_ONCE(__get_valid_kprobe(p)))
ret = -EINVAL;
mutex_unlock(&kprobe_mutex);

@@ -1614,7 +1617,7 @@ int register_kprobe(struct kprobe *p)
return PTR_ERR(addr);
p->addr = addr;

- ret = check_kprobe_rereg(p);
+ ret = warn_kprobe_rereg(p);
if (ret)
return ret;

@@ -1995,7 +1998,7 @@ int register_kretprobe(struct kretprobe *rp)
return ret;

/* If only rp->kp.addr is specified, check reregistering kprobes */
- if (rp->kp.addr && check_kprobe_rereg(&rp->kp))
+ if (rp->kp.addr && warn_kprobe_rereg(&rp->kp))
return -EINVAL;

if (kretprobe_blacklist_size) {