From 36992eb6b9b83f7f9cdc8e74fb5799d7b52e83e9 Mon Sep 17 00:00:00 2001
From: Zhang Yuchen <zhangyuchen.lcr@bytedance.com>
Date: Fri, 7 Oct 2022 17:26:17 +0800
Subject: [PATCH] ipmi: fix memleak when unload ipmi driver
Git-commit: 36992eb6b9b83f7f9cdc8e74fb5799d7b52e83e9
References: git-fixes
Patch-mainline: v6.2-rc1

After the IPMI disconnect problem, the memory kept rising and we tried
to unload the driver to free the memory. However, only part of the
free memory is recovered after the driver is uninstalled. Using
ebpf to hook free functions, we find that neither ipmi_user nor
ipmi_smi_msg is free, only ipmi_recv_msg is free.

We find that the deliver_smi_err_response call in clean_smi_msgs does
the destroy processing on each message from the xmit_msg queue without
checking the return value and free ipmi_smi_msg.

deliver_smi_err_response is called only at this location. Adding the
free handling has no effect.

To verify, try using ebpf to trace the free function.

  $ bpftrace -e 'kretprobe:ipmi_alloc_recv_msg {printf("alloc rcv
      %p\n",retval);} kprobe:free_recv_msg {printf("free recv %p\n",
      arg0)} kretprobe:ipmi_alloc_smi_msg {printf("alloc smi %p\n",
        retval);} kprobe:free_smi_msg {printf("free smi  %p\n",arg0)}'

Signed-off-by: Zhang Yuchen <zhangyuchen.lcr@bytedance.com>
Message-Id: <20221007092617.87597-4-zhangyuchen.lcr@bytedance.com>
[Fixed the comment above handle_one_recv_msg().]
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/char/ipmi/ipmi_msghandler.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 49a1707693c9..d5ee52be176d 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -3704,12 +3704,16 @@ static void deliver_smi_err_response(struct ipmi_smi *intf,
 				     struct ipmi_smi_msg *msg,
 				     unsigned char err)
 {
+	int rv;
 	msg->rsp[0] = msg->data[0] | 4;
 	msg->rsp[1] = msg->data[1];
 	msg->rsp[2] = err;
 	msg->rsp_size = 3;
-	/* It's an error, so it will never requeue, no need to check return. */
-	handle_one_recv_msg(intf, msg);
+
+	/* This will never requeue, but it may ask us to free the message. */
+	rv = handle_one_recv_msg(intf, msg);
+	if (rv == 0)
+		ipmi_free_smi_msg(msg);
 }
 
 static void cleanup_smi_msgs(struct ipmi_smi *intf)
-- 
2.39.2