linux-kernel - [char-misc-next] mei: allow map and unmap of client dma buffer only for disconnected client

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Date:   Thu, 18 Mar 2021 07:59:59 +0200
From:   Tomas Winkler <tomas.winkler@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Alexander Usyskin <alexander.usyskin@...el.com>,
        linux-kernel@...r.kernel.org,
        Tomas Winkler <tomas.winkler@...el.com>, stable@...r.kernel.org
Subject: [char-misc-next] mei: allow map and unmap of client dma buffer only for disconnected client

Allow map and unmap of the client dma buffer only when the client is not
connected. The functions return -EPROTO if the client is already connected.
This is to fix the race when traffic may start or stop when buffer
is not available.

Cc: <stable@...r.kernel.org> #v5.11+
Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
---
 drivers/misc/mei/client.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/misc/mei/client.c b/drivers/misc/mei/client.c
index 4378a9b25848..2cc370adb238 100644
--- a/drivers/misc/mei/client.c
+++ b/drivers/misc/mei/client.c
@@ -2286,8 +2286,8 @@ int mei_cl_dma_alloc_and_map(struct mei_cl *cl, const struct file *fp,
 	if (buffer_id == 0)
 		return -EINVAL;
 
-	if (!mei_cl_is_connected(cl))
-		return -ENODEV;
+	if (mei_cl_is_connected(cl))
+		return -EPROTO;
 
 	if (cl->dma_mapped)
 		return -EPROTO;
@@ -2327,9 +2327,7 @@ int mei_cl_dma_alloc_and_map(struct mei_cl *cl, const struct file *fp,
 
 	mutex_unlock(&dev->device_lock);
 	wait_event_timeout(cl->wait,
-			   cl->dma_mapped ||
-			   cl->status ||
-			   !mei_cl_is_connected(cl),
+			   cl->dma_mapped || cl->status,
 			   mei_secs_to_jiffies(MEI_CL_CONNECT_TIMEOUT));
 	mutex_lock(&dev->device_lock);
 
@@ -2376,8 +2374,9 @@ int mei_cl_dma_unmap(struct mei_cl *cl, const struct file *fp)
 		return -EOPNOTSUPP;
 	}
 
-	if (!mei_cl_is_connected(cl))
-		return -ENODEV;
+	/* do not allow unmap for connected client */
+	if (mei_cl_is_connected(cl))
+		return -EPROTO;
 
 	if (!cl->dma_mapped)
 		return -EPROTO;
@@ -2405,9 +2404,7 @@ int mei_cl_dma_unmap(struct mei_cl *cl, const struct file *fp)
 
 	mutex_unlock(&dev->device_lock);
 	wait_event_timeout(cl->wait,
-			   !cl->dma_mapped ||
-			   cl->status ||
-			   !mei_cl_is_connected(cl),
+			   !cl->dma_mapped || cl->status,
 			   mei_secs_to_jiffies(MEI_CL_CONNECT_TIMEOUT));
 	mutex_lock(&dev->device_lock);
 
-- 
2.26.3