linux-kernel - [char-misc-next 1/3] mei: protect mei_cl

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Message-Id: <20201029095444.957924-2-tomas.winkler@intel.com>
Date:   Thu, 29 Oct 2020 11:54:42 +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, stable@...r.kernel.org,
        Tomas Winkler <tomas.winkler@...el.com>
Subject: [char-misc-next 1/3] mei: protect mei_cl_mtu from null dereference

From: Alexander Usyskin <alexander.usyskin@...el.com>

A receive callback is queued while the client is still connected
but can still be called after the client was disconnected. Upon
disconnect cl->me_cl is set to NULL, hence we need to check
that ME client is not-NULL in mei_cl_mtu to avoid
null dereference.

Cc: <stable@...r.kernel.org>
Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
---
 drivers/misc/mei/client.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/client.h b/drivers/misc/mei/client.h
index 64143d4ec758..9e08a9843bba 100644
--- a/drivers/misc/mei/client.h
+++ b/drivers/misc/mei/client.h
@@ -182,11 +182,11 @@ static inline u8 mei_cl_me_id(const struct mei_cl *cl)
  *
  * @cl: host client
  *
- * Return: mtu
+ * Return: mtu or 0 if client is not connected
  */
 static inline size_t mei_cl_mtu(const struct mei_cl *cl)
 {
-	return cl->me_cl->props.max_msg_length;
+	return cl->me_cl ? cl->me_cl->props.max_msg_length : 0;
 }
 
 /**
-- 
2.25.4