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 <mhira...@kernel.org>
---
 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());

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