nci_rf_discover_ntf_packet() and nci_rf_intf_activated_ntf_packet() each
parse a notification into an on-stack struct (nci_rf_discover_ntf /
nci_rf_intf_activated_ntf) that is not initialised. The technology- and
activation-specific parameters are only extracted when the corresponding
length field is non-zero, so a notification that reports a zero length
leaves the relevant union uninitialised - and the handlers then read it:

 - discover: with rf_tech_specific_params_len == 0, nci_add_new_protocol()
   reads the uninitialised rf_tech_specific_params union (nfca_poll->
   nfcid1_len is used as a branch condition and a memcpy length) into
   ndev->targets;
 - activated: with rf_tech_specific_params_len == 0 the same union is read
   via nci_target_auto_activated(); with activation_params_len == 0 the
   activation_params union is read by nci_store_ats_nfc_iso_dep() into
   ndev->target_ats.

In each case the uninitialised bytes are subsequently exposed to user
space (NFC_CMD_GET_TARGET / NFC_ATTR_TARGET_ATS).

  BUG: KMSAN: uninit-value in nci_add_new_protocol+0x624/0x6c0
   nci_add_new_protocol+0x624/0x6c0
   nci_ntf_packet+0x25b2/0x3c30
   nci_rx_work+0x318/0x5d0
   process_scheduled_works+0x84b/0x17a0
   worker_thread+0xc10/0x11b0
   kthread+0x376/0x500
  Local variable ntf.i created at:
   nci_ntf_packet+0xbc2/0x3c30

Zero-initialise both on-stack notifications so the unions read back as
zero when the corresponding parameters are absent.

Fixes: 019c4fbaa790 ("NFC: Add NCI multiple targets support")
Fixes: e8c0dacd9836 ("NFC: Update names and structs to NCI spec 1.0 d18")
Link: https://lore.kernel.org/netdev/20260623172109.1105965-2-horms@kernel.org/ (local)
Cc: stable@vger.kernel.org
Assisted-by: Bynario AI
Signed-off-by: Samuel Page <redacted>
---
 net/nfc/nci/ntf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c
index c96512bb8653..274d9a4202c9 100644
--- a/net/nfc/nci/ntf.c
+++ b/net/nfc/nci/ntf.c

@@ -440,7 +440,7 @@ void nci_clear_target_list(struct nci_dev *ndev)
 static int nci_rf_discover_ntf_packet(struct nci_dev *ndev,
 				      const struct sk_buff *skb)
 {
-	struct nci_rf_discover_ntf ntf;
+	struct nci_rf_discover_ntf ntf = {};
 	const __u8 *data;
 	bool add_target = true;
 

@@ -688,7 +688,7 @@ static int nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
 					    const struct sk_buff *skb)
 {
 	struct nci_conn_info *conn_info;
-	struct nci_rf_intf_activated_ntf ntf;
+	struct nci_rf_intf_activated_ntf ntf = {};
 	const __u8 *data;
 	int err = NCI_STATUS_OK;
 

base-commit: a986fde914d88af47eb78fd29c5d1af7952c3500
-- 
2.54.0