[PATCH RESEND v2 2/2] nfc: st21nfca: prevent double completion of SE APDU request

[Joas Antonio dos Santos via B4 Relay <devnull+joasantonio108.gmail.com@kernel.org>]

From: Joas Antonio dos Santos <joasantonio108@gmail.com>

Use the spinlock added in the previous commit to prevent completing an
SE APDU request more than once.  Without this, the timeout work handler
(st21nfca_se_wt_work) and the EVT_TRANSMIT_DATA event handler can race
and both invoke the callback, leading to a use-after-free or double-free
of the callback context.

Check bwi_active under the lock in both completion paths and bail out if
the request was already completed.  Also reject a new SE APDU request in
st21nfca_hci_se_io() while one is already in progress by returning
-EBUSY.

Found by LLM-assisted manual code review.

Fixes: 2130fb97fecf ("NFC: st21nfca: Adding support for secure element")
Cc: Simon Horman <horms@kernel.org>
Signed-off-by: Joas Antonio dos Santos <joasantonio108@gmail.com>
---
 drivers/nfc/st21nfca/se.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/nfc/st21nfca/se.c b/drivers/nfc/st21nfca/se.c
index 03a30f797ff8..3be77420e956 100644
--- a/drivers/nfc/st21nfca/se.c
+++ b/drivers/nfc/st21nfca/se.c
@@ -228,6 +228,10 @@ int st21nfca_hci_se_io(struct nfc_hci_dev *hdev, u32 se_idx,
 	switch (se_idx) {
 	case ST21NFCA_ESE_HOST_ID:
 		spin_lock(&info->se_info.se_lock);
+		if (info->se_info.bwi_active) {
+			spin_unlock(&info->se_info.se_lock);
+			return -EBUSY;
+		}
 		info->se_info.cb = cb;
 		info->se_info.cb_context = cb_context;
 		info->se_info.bwi_active = true;
@@ -269,6 +273,10 @@ static void st21nfca_se_wt_work(struct work_struct *work)
 						se_info.timeout_work);
 
 	spin_lock(&info->se_info.se_lock);
+	if (!info->se_info.bwi_active) {
+		spin_unlock(&info->se_info.se_lock);
+		return;
+	}
 	info->se_info.bwi_active = false;
 	cb = info->se_info.cb;
 	cb_context = info->se_info.cb_context;
@@ -395,6 +403,10 @@ int st21nfca_apdu_reader_event_received(struct nfc_hci_dev *hdev,
 		cancel_work_sync(&info->se_info.timeout_work);
 
 		spin_lock(&info->se_info.se_lock);
+		if (!info->se_info.bwi_active) {
+			spin_unlock(&info->se_info.se_lock);
+			break;
+		}
 		info->se_info.bwi_active = false;
 		cb = info->se_info.cb;
 		cb_context = info->se_info.cb_context;

-- 
2.43.0