From 513125f30a05b4ad3408d5f4efd36d2c6ba10744 Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Sun, 1 Oct 2023 16:08:43 +0200
Subject: mach_msg: Fix checking reception size

We need to check against the actual user size that will be used, not the
current kernel size.

Usually userland uses amply-large reception buffer, but better be exact.
---
 kern/ipc_mig.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kern/ipc_mig.c b/kern/ipc_mig.c
index df8a9467..d26d2c6d 100644
--- a/kern/ipc_mig.c
+++ b/kern/ipc_mig.c
@@ -198,7 +198,7 @@ mach_msg(
 
 		kmsg->ikm_header.msgh_seqno = seqno;
 
-		if (rcv_size < kmsg->ikm_header.msgh_size) {
+		if (rcv_size < msg_usize(&kmsg->ikm_header)) {
 			ipc_kmsg_copyout_dest(kmsg, space);
 			ipc_kmsg_put_to_kernel(msg, kmsg, sizeof *msg);
 			return MACH_RCV_TOO_LARGE;
-- 
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