linux-kernel - [PATCH v1] firmware: arm_scmi: Fix NULL pointer dereference in mailbox_clear

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Message-Id: <ED5DC8DB-AE81-4380-8AE5-588F370CD4B0@gmail.com>
Date:   Wed, 30 Aug 2023 01:07:47 +0800
From:   Qiujun Huang <hqjagain@...il.com>
To:     sudeep.holla@....com, cristian.marussi@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] firmware: arm_scmi: Fix NULL pointer dereference in
 mailbox_clear_channel

There is a race between the failure of probe and rx_callback (due to a
delayed response).

scmi_probe
scmi_acquire_protocal
do_xfer
 timeout
mailbox_chan_free
                                                    <--- delay response
                                                           rx_callback
mbox_free_channel
cinfo->transport_info = NULL
                                                          mailbox_clear_channel
                                                         dereference cinfo->transport_info

This patch check for it, and clear the channel at mailbox_chan_free.

Signed-off-by: Qiujun Huang <hqjagain@...il.com>
---
 drivers/firmware/arm_scmi/mailbox.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/mailbox.c b/drivers/firmware/arm_scmi/mailbox.c
index 19246ed1f01f..32c5fe0b8c29 100644
--- a/drivers/firmware/arm_scmi/mailbox.c
+++ b/drivers/firmware/arm_scmi/mailbox.c
@@ -230,6 +230,7 @@ static int mailbox_chan_free(int id, void *p, void *data)
 		smbox->chan = NULL;
 		smbox->chan_receiver = NULL;
 		smbox->cinfo = NULL;
+		shmem_clear_channel(smbox->shmem);
 	}

 	return 0;
@@ -284,7 +285,8 @@ static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
 {
 	struct scmi_mailbox *smbox = cinfo->transport_info;

-	shmem_clear_channel(smbox->shmem);
+	if (smbox)
+		shmem_clear_channel(smbox->shmem);
 }

 static bool
--
2.30.2