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

[Masami Hiramatsu]

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@xxxxxxxxxx>
---
 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());