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Fri, 10 Jul 2026 09:52:04 +0000 Message-ID: <8e4f59b8-0354-401e-89fd-5f8686587bf0@intel.com> Date: Fri, 10 Jul 2026 11:51:58 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next] nfc: digital: Do not dump a NULL response in command completion To: Linmao Li CC: Simon Horman , Mark Greer , , , , David Heidelberg , "David S . Miller" , Eric Dumazet , "Jakub Kicinski" , Paolo Abeni References: <20260710061254.80975-1-lilinmao@kylinos.cn> From: Przemek Kitszel Content-Language: en-US In-Reply-To: <20260710061254.80975-1-lilinmao@kylinos.cn> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: DB8PR04CA0012.eurprd04.prod.outlook.com (2603:10a6:10:110::22) To LV3PR11MB8508.namprd11.prod.outlook.com (2603:10b6:408:1b4::8) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV3PR11MB8508:EE_|SJ2PR11MB7518:EE_ X-MS-Office365-Filtering-Correlation-Id: 9e96bace-875a-41d2-2785-08dede68e564 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|1800799024|366016|23010399003|376014|18002099003|22082099003|3023799007|56012099006|11063799006|6133799003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV3PR11MB8508.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(7416014)(1800799024)(366016)(23010399003)(376014)(18002099003)(22082099003)(3023799007)(56012099006)(11063799006)(6133799003);DIR:OUT;SFP:1101; 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However, a driver can legitimately complete a > command with no response skb at all. > > digital_tg_send_psl_res() is the only caller that passes timeout=0, > meaning no response is expected once the command has been transmitted. > On that path trf7970a completes the command with > > trf->rx_skb = ERR_PTR(0); > > which evaluates to NULL. IS_ERR(NULL) is false, so the NULL response > passes the !IS_ERR() check and cmd->resp->data and cmd->resp->len are > dereferenced whenever the debug print site is enabled. The driver > guards its own dump with "trf->rx_skb && !IS_ERR(trf->rx_skb)"; the > digital layer is missing the NULL half of that test. > > Use IS_ERR_OR_NULL() so that NULL responses are skipped as well. The > callback on that path, digital_tg_send_psl_res_complete(), never > dereferences resp and dev_kfree_skb() accepts NULL, so only the debug > dump needs fixing. > > Fixes: 59ee2361c924 ("NFC Digital: Implement driver commands mechanism") > Signed-off-by: Linmao Li Reviewed-by: Przemek Kitszel > --- > A separate cleanup patch, "nfc: trf7970a: Use NULL when no response is > expected", replaces that ERR_PTR(0) with a plain NULL. It does not > change behaviour (ERR_PTR(0) is NULL), so this fix is needed either way; > if that patch lands first, read "trf->rx_skb = NULL;" above. > > Link: https://patch.msgid.link/20260706075743.564658-1-lilinmao@kylinos.cn > > net/nfc/digital_core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/nfc/digital_core.c b/net/nfc/digital_core.c > index 7cb1e6aaae90..18236221d898 100644 > --- a/net/nfc/digital_core.c > +++ b/net/nfc/digital_core.c > @@ -127,7 +127,7 @@ static void digital_wq_cmd_complete(struct work_struct *work) > > mutex_unlock(&ddev->cmd_lock); > > - if (!IS_ERR(cmd->resp)) > + if (!IS_ERR_OR_NULL(cmd->resp)) > print_hex_dump_debug("DIGITAL RX: ", DUMP_PREFIX_NONE, 16, 1, > cmd->resp->data, cmd->resp->len, false); >