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

[Masami Hiramatsu]

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@xxxxxxxxxx>
Fixes: f47cd9b553aa ("kprobes: kretprobe user entry-handler")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 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;