linux-kernel - [RFC PATCH tip/master 3/3] kprobes: Limit kretprobe maximum instances

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Date:   Wed, 29 Mar 2017 14:24:23 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Alban Crequy <alban.crequy@...il.com>,
        Alban Crequy <alban@...volk.io>,
        Alexei Starovoitov <ast@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Omar Sandoval <osandov@...com>, linux-doc@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        iago@...volk.io, michael@...volk.io,
        Dorau Lukasz <lukasz.dorau@...el.com>, systemtap@...rceware.org
Subject: [RFC PATCH tip/master 3/3] kprobes: Limit kretprobe maximum instances

Limit kretprobe maximum instance up to MAXACTIVE_ALLOC.
Without this limit, kretprobe user can specify huge number
(e.g. forget to zero-fill struct kretprobe) to maxactive
and may cause out-of-memory.

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

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 75c5390..f1bebcf 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1942,6 +1942,9 @@ int register_kretprobe(struct kretprobe *rp)
 	rp->kp.break_handler = NULL;
 
 	/* Pre-allocate memory for max kretprobe instances */
+	if (rp->maxactive > KRETPROBE_MAXACTIVE_ALLOC)
+		return -E2BIG;
+
 	if (rp->maxactive <= 0) {
 #ifdef CONFIG_PREEMPT
 		rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());