[PATCH 4.4 41/52] kprobes: Limit max data_size of the kretprobe instances

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Masami Hiramatsu <mhiramat@kernel.org>

commit 6bbfa44116689469267f1a6e3d233b52114139d2 upstream.

The 'kprobe::data_size' is unsigned, thus it can not be negative.  But if
user sets it enough big number (e.g. (size_t)-8), the result of 'data_size
+ sizeof(struct kretprobe_instance)' becomes smaller than sizeof(struct
kretprobe_instance) or zero. In result, the kretprobe_instance are
allocated without enough memory, and kretprobe accesses outside of
allocated memory.

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

Link: https://lkml.kernel.org/r/163836995040.432120.10322772773821182925.stgit@devnote2

Cc: stable@vger.kernel.org
Fixes: f47cd9b553aa ("kprobes: kretprobe user entry-handler")
Reported-by: zhangyue <zhangyue1@kylinos.cn>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/kprobes.h |    2 ++
 kernel/kprobes.c        |    3 +++
 2 files changed, 5 insertions(+)

--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -192,6 +192,8 @@ struct kretprobe {
 	raw_spinlock_t lock;
 };
 
+#define KRETPROBE_MAX_DATA_SIZE	4096
+
 struct kretprobe_instance {
 	struct hlist_node hlist;
 	struct kretprobe *rp;
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1899,6 +1899,9 @@ int register_kretprobe(struct kretprobe
 		}
 	}
 
+	if (rp->data_size > KRETPROBE_MAX_DATA_SIZE)
+		return -E2BIG;
+
 	rp->kp.pre_handler = pre_handler_kretprobe;
 	rp->kp.post_handler = NULL;
 	rp->kp.fault_handler = NULL;