netdev - [PATCH V2 net 12/12] net: ena: ena-com.c: prevent NULL pointer dereference

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Message-ID: <20200211151751.29718-13-sameehj@amazon.com>
Date:   Tue, 11 Feb 2020 15:17:51 +0000
From:   <sameehj@...zon.com>
To:     <davem@...emloft.net>, <netdev@...r.kernel.org>
CC:     Arthur Kiyanovski <akiyano@...zon.com>, <dwmw@...zon.com>,
        <zorik@...zon.com>, <matua@...zon.com>, <saeedb@...zon.com>,
        <msw@...zon.com>, <aliguori@...zon.com>, <nafea@...zon.com>,
        <gtzalik@...zon.com>, <netanel@...zon.com>, <alisaidi@...zon.com>,
        <benh@...zon.com>, <sameehj@...zon.com>, <ndagan@...zon.com>
Subject: [PATCH V2 net 12/12] net: ena: ena-com.c: prevent NULL pointer dereference

From: Arthur Kiyanovski <akiyano@...zon.com>

comp_ctx can be NULL in a very rare case when an admin command is executed
during the execution of ena_remove().

The bug scenario is as follows:

* ena_destroy_device() sets the comp_ctx to be NULL
* An admin command is executed before executing unregister_netdev(),
  this can still happen because our device can still receive callbacks
  from the netdev infrastructure such as ethtool commands.
* When attempting to access the comp_ctx, the bug occurs since it's set
  to NULL

Fix:
Added a check that comp_ctx is not NULL

Fixes: 1738cd3ed342 ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Sameeh Jubran <sameehj@...zon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@...zon.com>
---
 drivers/net/ethernet/amazon/ena/ena_com.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c b/drivers/net/ethernet/amazon/ena/ena_com.c
index 0f93d1092..1fb58f9ad 100644
--- a/drivers/net/ethernet/amazon/ena/ena_com.c
+++ b/drivers/net/ethernet/amazon/ena/ena_com.c
@@ -200,6 +200,11 @@ static void comp_ctxt_release(struct ena_com_admin_queue *queue,
 static struct ena_comp_ctx *get_comp_ctxt(struct ena_com_admin_queue *queue,
 					  u16 command_id, bool capture)
 {
+	if (unlikely(!queue->comp_ctx)) {
+		pr_err("Completion context is NULL\n");
+		return NULL;
+	}
+
 	if (unlikely(command_id >= queue->q_depth)) {
 		pr_err("command id is larger than the queue size. cmd_id: %u queue size %d\n",
 		       command_id, queue->q_depth);
-- 
2.24.1.AMZN