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

[Tomas Winkler]

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: <sta...@vger.kernel.org> #v5.11+
Signed-off-by: Tomas Winkler <tomas.wink...@intel.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