Re: [PATCH net-next] nfc: digital: Do not dump a NULL response in command completion
From: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Date: 2026-07-10 09:52:13
Also in:
lkml, oe-linux-nfc
On 7/10/26 08:12, Linmao Li wrote:
digital_wq_cmd_complete() dumps the response data whenever cmd->resp is
not an error pointer. 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 <redacted>Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
quoted hunk ↗ jump to hunk
--- 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);