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client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by BN3PEPF0000B372.mail.protection.outlook.com (10.167.243.169) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.315.0 via Frontend Transport; Fri, 7 Aug 2026 06:36:31 +0000 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.41; Fri, 7 Aug 2026 01:36:30 -0500 Received: from xhdipdslab46.xilinx.com (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.41 via Frontend Transport; Fri, 7 Aug 2026 01:36:27 -0500 From: Abhijit Gangurde To: , CC: , , , , , "Abhijit Gangurde" , Prasanna Kumar T S M Subject: [PATCH 1/1] cdx: fix use-after-free in cdx_mcdi_process_cmd after timeout Date: Fri, 7 Aug 2026 12:06:09 +0530 Message-ID: <20260807063609.2413865-1-abhijit.gangurde@amd.com> X-Mailer: git-send-email 2.44.4 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B372:EE_|CY8PR12MB7434:EE_ X-MS-Office365-Filtering-Correlation-Id: 3f6fb60c-1c78-4461-a2ce-08def44e37f1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|36860700016|376014|23010399003|18002099003|11063799006|56012099006|3023799007|10067099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: QihBpwL48bsLY7A/7EHhc56t00BdaSYa6MtbLKpbyU3IAu0dF46QYNKcwj62OHHYQ80hMjznrOIWZ0GqpkMxz25lke1HHUj2Ww8eeJm/KXb4Mil5NCxakbSES1zt2UvDKYmaDE52Yxv0bKcv8WM3pA8/4IW2sS6MbITsAJ4IRFAWQVbG93umW4aJyUsXR97JPCV7Di2oJDtvmlI5OC23DgrnbmU6DnMFaLPwl4i20yB/MdBd+Y+rSjqhsPwvFsRqgjKxpdvqjRJXlWXr9bY4EIJE2VuSB/jEKzd9zqf8rC+EMt9RD+exrXMI/+i4Z2ty6B86oo+VBopPxknJbJi4kQuCHRQdxdL5f8rhEjIukIQFcCb72PvxbotSy5XXJFqUym1Il4lySBRDRKgiaRPTYSpVohct1dbflmazXFQ2GdReAzQg8ML7Td5nnRCQ7B6a X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Aug 2026 06:36:31.6002 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 3f6fb60c-1c78-4461-a2ce-08def44e37f1 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B372.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7434 When an MCDI command times out, cdx_mcdi_timeout_cmd() frees the cmd via cdx_mcdi_remove_cmd() but does not clear mcdi->seq_held_by[] or mcdi->db_held_by. If the firmware responds after the timeout, cdx_mcdi_process_cmd() dereferences the freed cmd pointer leading to a use-after-free. clear the seq_held_by and db_held_by in the timeout path, and add an extra kref to handle the race where the response arrives concurrently with the timeout handler. Fixes: eb96b740192b ("cdx: add MCDI protocol interface for firmware interaction") Co-developed-by: Prasanna Kumar T S M Signed-off-by: Prasanna Kumar T S M Signed-off-by: Abhijit Gangurde --- drivers/cdx/controller/mcdi.c | 28 +++++++++++++++++----------- 1 file changed, 17 insertions(+), 11 deletions(-) diff --git a/drivers/cdx/controller/mcdi.c b/drivers/cdx/controller/mcdi.c index 34a07d6f41a0..ef46aeddcf01 100644 --- a/drivers/cdx/controller/mcdi.c +++ b/drivers/cdx/controller/mcdi.c @@ -405,6 +405,11 @@ static void cdx_mcdi_cancel_cmd(struct cdx_mcdi *cdx, struct cdx_mcdi_cmd *cmd) return; mutex_lock(&mcdi->iface_lock); + if (cmd->state == MCDI_STATE_FINISHED) { + mutex_unlock(&mcdi->iface_lock); + return; + } + cdx_mcdi_timeout_cmd(mcdi, cmd, &cleanup_list); mutex_unlock(&mcdi->iface_lock); cdx_mcdi_process_cleanup_list(cdx, &cleanup_list); @@ -473,6 +478,8 @@ static int cdx_mcdi_rpc_sync(struct cdx_mcdi *cdx, unsigned int cmd, wait_data->outlen = outlen; kref_init(&cmd_item->ref); + /* Claim an extra ref in case response comes after timeout */ + kref_get(&cmd_item->ref); cmd_item->quiet = quiet; cmd_item->cookie = (unsigned long)wait_data; cmd_item->completer = &cdx_mcdi_rpc_completer; @@ -506,6 +513,7 @@ static int cdx_mcdi_rpc_sync(struct cdx_mcdi *cdx, unsigned int cmd, out: kref_put(&wait_data->ref, cdx_mcdi_blocking_data_release); + kref_put(&cmd_item->ref, cdx_mcdi_cmd_release); return rc; } @@ -611,17 +619,10 @@ void cdx_mcdi_process_cmd(struct cdx_mcdi *cdx, struct cdx_dword *outbuf, int le mutex_lock(&mcdi->iface_lock); cmd = mcdi->seq_held_by[respseq]; - if (cmd) { - if (cmd->state == MCDI_STATE_FINISHED) { - mutex_unlock(&mcdi->iface_lock); - kref_put(&cmd->ref, cdx_mcdi_cmd_release); - return; - } - + if (cmd) cdx_mcdi_complete_cmd(mcdi, cmd, outbuf, len, &cleanup_list); - } else { + else pr_err("MC response unexpected for seq : %0X\n", respseq); - } mutex_unlock(&mcdi->iface_lock); @@ -734,7 +735,7 @@ static bool cdx_mcdi_complete_cmd(struct cdx_mcdi_iface *mcdi, completed = true; } - /* free sequence number and buffer */ + /* free sequence number */ mcdi->seq_held_by[cmd->seq] = NULL; cdx_mcdi_start_or_queue(mcdi, rc != MC_CMD_ERR_QUEUE_FULL); @@ -759,6 +760,11 @@ static void cdx_mcdi_timeout_cmd(struct cdx_mcdi_iface *mcdi, cmd->rc = -ETIMEDOUT; cdx_mcdi_remove_cmd(mcdi, cmd, cleanup_list); + /* free sequence number */ + if (mcdi->seq_held_by[cmd->seq] == cmd) + mcdi->seq_held_by[cmd->seq] = NULL; + if (mcdi->db_held_by == cmd) + mcdi->db_held_by = NULL; cdx_mcdi_mode_fail(cdx, cleanup_list); } @@ -821,7 +827,7 @@ cdx_mcdi_rpc_async(struct cdx_mcdi *cdx, unsigned int cmd, cdx_mcdi_async_completer *complete, unsigned long cookie) { struct cdx_mcdi_cmd *cmd_item = - kmalloc(sizeof(struct cdx_mcdi_cmd) + inlen, GFP_ATOMIC); + kzalloc(sizeof(struct cdx_mcdi_cmd) + inlen, GFP_ATOMIC); if (!cmd_item) return -ENOMEM; -- 2.44.4