kprobes: Limit max data_size of the kretprobe instances

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>

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index e974caf..8c8f7a4 100644 (file)
--- 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 e9db0c8..21eccc9 100644 (file)
--- 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;