[PATCH v2] nfc: nci: fix use of uninitialized memory in CORE_INIT_RSP parsing
From: Yun Zhou <hidden>
Date: 2026-05-22 02:14:32
Also in:
netdev, oe-linux-nfc
Subsystem:
networking [general], nfc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Heidelberg, Linus Torvalds
nci_core_init_rsp_packet_v1() and nci_core_init_rsp_packet_v2() parse the CORE_INIT_RSP packet without validating that the skb contains enough data. A malformed response (e.g. injected via virtual_ncidev) can declare a large num_supported_rf_interfaces while providing insufficient data, causing reads of uninitialized slab memory. This is later used in nci_init_complete_req(), triggering a KMSAN uninit-value warning. Add skb length checks before accessing packet fields: - Validate the skb has at least 1 byte for the status field. - Validate the skb can hold the fixed-size header before parsing. - In v2, bounds-check each variable-length rf_interface entry and its extension parameters within the parsing loop. - In v1, verify the skb is large enough for both the variable-length rf_interfaces array and the trailing rsp_2 structure. Reported-by: syzbot+46ca2592193f2fb3debc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=46ca2592193f2fb3debc Fixes: bcd684aace34 ("net/nfc/nci: Support NCI 2.x initial sequence") Signed-off-by: Yun Zhou <redacted> --- v2: - Validate the skb has at least 1 byte for the status field. - Move the fixed-size header check after the status access. - Add Closes: link after Reported-by net/nfc/nci/rsp.c | 37 +++++++++++++++++++++++++++++++++++-- 1 file changed, 35 insertions(+), 2 deletions(-)
diff --git a/net/nfc/nci/rsp.c b/net/nfc/nci/rsp.c
index 9eeb862825c5..61fbe31b427e 100644
--- a/net/nfc/nci/rsp.c
+++ b/net/nfc/nci/rsp.c@@ -50,11 +50,19 @@ static u8 nci_core_init_rsp_packet_v1(struct nci_dev *ndev, const struct nci_core_init_rsp_1 *rsp_1 = (void *)skb->data; const struct nci_core_init_rsp_2 *rsp_2; + /* Ensure that the status field can be accessed. */ + if (skb->len < 1) + return NCI_STATUS_SYNTAX_ERROR; + pr_debug("status 0x%x\n", rsp_1->status); if (rsp_1->status != NCI_STATUS_OK) return rsp_1->status; + /* Success response must contain the full fixed-size header */ + if (skb->len < sizeof(*rsp_1)) + return NCI_STATUS_SYNTAX_ERROR; + ndev->nfcc_features = __le32_to_cpu(rsp_1->nfcc_features); ndev->num_supported_rf_interfaces = rsp_1->num_supported_rf_interfaces;
@@ -62,6 +70,10 @@ static u8 nci_core_init_rsp_packet_v1(struct nci_dev *ndev, min((int)ndev->num_supported_rf_interfaces, NCI_MAX_SUPPORTED_RF_INTERFACES); + if (skb->len < sizeof(*rsp_1) + rsp_1->num_supported_rf_interfaces + + sizeof(*rsp_2)) + return NCI_STATUS_SYNTAX_ERROR; + memcpy(ndev->supported_rf_interfaces, rsp_1->supported_rf_interfaces, ndev->num_supported_rf_interfaces);
@@ -87,15 +99,26 @@ static u8 nci_core_init_rsp_packet_v2(struct nci_dev *ndev, const struct sk_buff *skb) { const struct nci_core_init_rsp_nci_ver2 *rsp = (void *)skb->data; - const u8 *supported_rf_interface = rsp->supported_rf_interfaces; + const u8 *supported_rf_interface; + const u8 *skb_end = skb->data + skb->len; u8 rf_interface_idx = 0; u8 rf_extension_cnt = 0; + /* Ensure that the status field can be accessed. */ + if (skb->len < 1) + return NCI_STATUS_SYNTAX_ERROR; + pr_debug("status %x\n", rsp->status); if (rsp->status != NCI_STATUS_OK) return rsp->status; + /* Success response must contain the full fixed-size header */ + if (skb->len < sizeof(*rsp)) + return NCI_STATUS_SYNTAX_ERROR; + + supported_rf_interface = rsp->supported_rf_interfaces; + ndev->nfcc_features = __le32_to_cpu(rsp->nfcc_features); ndev->num_supported_rf_interfaces = rsp->num_supported_rf_interfaces;
@@ -104,13 +127,23 @@ static u8 nci_core_init_rsp_packet_v2(struct nci_dev *ndev, NCI_MAX_SUPPORTED_RF_INTERFACES); while (rf_interface_idx < ndev->num_supported_rf_interfaces) { - ndev->supported_rf_interfaces[rf_interface_idx++] = *supported_rf_interface++; + /* Each entry: [rf_interface_type (1B)] [ext_count (1B)] [ext...] */ + if (supported_rf_interface + 2 > skb_end) + break; + ndev->supported_rf_interfaces[rf_interface_idx] = *supported_rf_interface++; /* skip rf extension parameters */ rf_extension_cnt = *supported_rf_interface++; + if (supported_rf_interface + rf_extension_cnt > skb_end) + break; + + /* Only count the entry after full validation */ + rf_interface_idx++; supported_rf_interface += rf_extension_cnt; } + ndev->num_supported_rf_interfaces = rf_interface_idx; + ndev->max_logical_connections = rsp->max_logical_connections; ndev->max_routing_table_size = __le16_to_cpu(rsp->max_routing_table_size);
--
2.43.0