linux-kernel - [PATCH 1/2] cxl/core: Fix initialization of mbox_cmd.size

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Date: Mon,  1 Apr 2024 18:10:55 +0900
From: Kwangjin Ko <kwangjin.ko@...com>
To: dave@...olabs.net,
	jonathan.cameron@...wei.com,
	dave.jiang@...el.com,
	alison.schofield@...el.com,
	vishal.l.verma@...el.com,
	ira.weiny@...el.com,
	dan.j.williams@...el.com
Cc: linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	kernel_team@...ynix.com
Subject: [PATCH 1/2] cxl/core: Fix initialization of mbox_cmd.size_out in get event

Since mbox_cmd.size_out is overwritten with the actual output size in
the function below, it needs to be initialized every time.

cxl_internal_send_cmd -> __cxl_pci_mbox_send_cmd

Problem scenario:

1) The size_out variable is initially set to the size of the mailbox
2) Read an event
   - size_out is set to 160 bytes (header 32B + one event 128B)
   - Two event are created while read
3) Read two events
   - size_out is still set as 160 bytes
   - Although the value of out_len is 288 bytes, only 160 bytes are
     copied from the mailbox register to the local variable
   - record_count is set to 2
   - Acessing records[1] causes a buffer overflow

Signed-off-by: Kwangjin Ko <kwangjin.ko@...com>
---
 drivers/cxl/core/mbox.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 9adda4795eb7..a38531a055c8 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -958,13 +958,14 @@ static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
 		.payload_in = &log_type,
 		.size_in = sizeof(log_type),
 		.payload_out = payload,
-		.size_out = mds->payload_size,
 		.min_out = struct_size(payload, records, 0),
 	};
 
 	do {
 		int rc, i;
 
+		mbox_cmd.size_out = mds->payload_size;
+
 		rc = cxl_internal_send_cmd(mds, &mbox_cmd);
 		if (rc) {
 			dev_err_ratelimited(dev,

base-commit: 39cd87c4eb2b893354f3b850f916353f2658ae6f
-- 
2.34.1