linux-kernel - [PATCH] kprobes: Limit max data_size of the kretprobe instances

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Message-Id: <163836995040.432120.10322772773821182925.stgit@devnote2>
Date:   Wed,  1 Dec 2021 23:45:50 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        zhangyue <zhangyue1@...inos.cn>, naveen.n.rao@...ux.ibm.com,
        anil.s.keshavamurthy@...el.com, davem@...emloft.net,
        mhiramat@...nel.org
Subject: [PATCH] kprobes: Limit max data_size of the kretprobe instances

The kretprobe::data_size is unsigned (size_t) but it is
used as 'data_size + sizeof(struct kretprobe_instance)'.
Thus, it can be smaller than sizeof(struct kretprobe_instance)
while allocating memory for the kretprobe_instance.

To avoid this issue, introduce a max limitation of the
kretprobe::data_size. 4KB per instance should be OK.

Reported-by: zhangyue <zhangyue1@...inos.cn>
Fixes: f47cd9b553aa ("kprobes: kretprobe user entry-handler")
Cc: stable@...r.kernel.org
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 include/linux/kprobes.h |    2 ++
 kernel/kprobes.c        |    3 +++
 2 files changed, 5 insertions(+)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index e974caf39d3e..8c8f7a4d93af 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -153,6 +153,8 @@ struct kretprobe {
 	struct kretprobe_holder *rph;
 };
 
+#define KRETPROBE_MAX_DATA_SIZE	4096
+
 struct kretprobe_instance {
 	union {
 		struct freelist_node freelist;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index e9db0c810554..21eccc961bba 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2086,6 +2086,9 @@ int register_kretprobe(struct kretprobe *rp)
 		}
 	}
 
+	if (rp->data_size > KRETPROBE_MAX_DATA_SIZE)
+		return -E2BIG;
+
 	rp->kp.pre_handler = pre_handler_kretprobe;
 	rp->kp.post_handler = NULL;