From: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx> Bluetooth Core Specification v5.2, Vol. 3, Part A, section 1.4, table 1.1: 'Start Fragments always either begin with the first octet of the Basic L2CAP header of a PDU or they have a length of zero (see [Vol 2] Part B, Section 6.6.2).' Apparently this was changed by the following errata: https://www.bluetooth.org/tse/errata_view.cfm?errata_id=10216 Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx> --- include/net/bluetooth/l2cap.h | 1 + net/bluetooth/l2cap_core.c | 118 +++++++++++++++++++++++++++------- 2 files changed, 94 insertions(+), 25 deletions(-) diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index 1d1232917de7..61800a7b6192 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -207,6 +207,7 @@ struct l2cap_hdr { __le16 len; __le16 cid; } __packed; +#define L2CAP_LEN_SIZE 2 #define L2CAP_HDR_SIZE 4 #define L2CAP_ENH_HDR_SIZE 6 #define L2CAP_EXT_HDR_SIZE 8 diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 17b87b57a175..a24183734bd9 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -8276,10 +8276,73 @@ static void l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt) mutex_unlock(&conn->chan_lock); } +/* Append fragment into frame respecting the maximum len of rx_skb */ +static int l2cap_recv_frag(struct l2cap_conn *conn, struct sk_buff *skb, + u16 len) +{ + if (!conn->rx_skb) { + /* Allocate skb for the complete frame (with header) */ + conn->rx_skb = bt_skb_alloc(len, GFP_KERNEL); + if (!conn->rx_skb) + return -ENOMEM; + /* Init rx_len */ + conn->rx_len = len; + } + + /* Copy as much as the rx_skb can hold */ + len = min_t(u16, len, skb->len); + skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, len), len); + skb_pull(skb, len); + conn->rx_len -= len; + + return len; +} + +static int l2cap_recv_len(struct l2cap_conn *conn, struct sk_buff *skb) +{ + struct sk_buff *rx_skb; + int len; + + /* Append just enough to complete the header */ + len = l2cap_recv_frag(conn, skb, L2CAP_LEN_SIZE - conn->rx_skb->len); + + /* If header could not be read just continue */ + if (len < 0 || conn->rx_skb->len < L2CAP_LEN_SIZE) + return len; + + rx_skb = conn->rx_skb; + len = get_unaligned_le16(rx_skb->data); + + /* Check if rx_skb has enough space to received all fragments */ + if (len + (L2CAP_HDR_SIZE - L2CAP_LEN_SIZE) <= skb_tailroom(rx_skb)) { + /* Update expected len */ + conn->rx_len = len + (L2CAP_HDR_SIZE - L2CAP_LEN_SIZE); + return L2CAP_LEN_SIZE; + } + + /* Reset conn->rx_skb since it will need to be reallocated in order to + * fit all fragments. + */ + conn->rx_skb = NULL; + + /* Reallocates rx_skb using the exact expected length */ + len = l2cap_recv_frag(conn, rx_skb, + len + (L2CAP_HDR_SIZE - L2CAP_LEN_SIZE)); + kfree_skb(rx_skb); + + return len; +} + +static void l2cap_recv_reset(struct l2cap_conn *conn) +{ + kfree_skb(conn->rx_skb); + conn->rx_skb = NULL; + conn->rx_len = 0; +} + void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) { struct l2cap_conn *conn = hcon->l2cap_data; - struct l2cap_hdr *hdr; int len; /* For AMP controller do not create l2cap conn */ @@ -8298,23 +8361,23 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) case ACL_START: case ACL_START_NO_FLUSH: case ACL_COMPLETE: - if (conn->rx_len) { + if (conn->rx_skb) { BT_ERR("Unexpected start frame (len %d)", skb->len); - kfree_skb(conn->rx_skb); - conn->rx_skb = NULL; - conn->rx_len = 0; + l2cap_recv_reset(conn); l2cap_conn_unreliable(conn, ECOMM); } - /* Start fragment always begin with Basic L2CAP header */ - if (skb->len < L2CAP_HDR_SIZE) { - BT_ERR("Frame is too short (len %d)", skb->len); - l2cap_conn_unreliable(conn, ECOMM); - goto drop; + /* Start fragment may not contain the L2CAP length so just + * copy the initial byte when that happens and use conn->mtu as + * expected length. + */ + if (skb->len < L2CAP_LEN_SIZE) { + if (l2cap_recv_frag(conn, skb, conn->mtu) < 0) + goto drop; + return; } - hdr = (struct l2cap_hdr *) skb->data; - len = __le16_to_cpu(hdr->len) + L2CAP_HDR_SIZE; + len = get_unaligned_le16(skb->data) + L2CAP_HDR_SIZE; if (len == skb->len) { /* Complete frame received */ @@ -8331,38 +8394,43 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) goto drop; } - /* Allocate skb for the complete frame (with header) */ - conn->rx_skb = bt_skb_alloc(len, GFP_KERNEL); - if (!conn->rx_skb) + /* Append fragment into frame (with header) */ + if (l2cap_recv_frag(conn, skb, len) < 0) goto drop; - skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len), - skb->len); - conn->rx_len = len - skb->len; break; case ACL_CONT: BT_DBG("Cont: frag len %d (expecting %d)", skb->len, conn->rx_len); - if (!conn->rx_len) { + if (!conn->rx_skb) { BT_ERR("Unexpected continuation frame (len %d)", skb->len); l2cap_conn_unreliable(conn, ECOMM); goto drop; } + /* Complete the L2CAP length if it has not been read */ + if (conn->rx_skb->len < L2CAP_LEN_SIZE) { + if (l2cap_recv_len(conn, skb) < 0) { + l2cap_conn_unreliable(conn, ECOMM); + goto drop; + } + + /* Header still could not be read just continue */ + if (conn->rx_skb->len < L2CAP_LEN_SIZE) + return; + } + if (skb->len > conn->rx_len) { BT_ERR("Fragment is too long (len %d, expected %d)", skb->len, conn->rx_len); - kfree_skb(conn->rx_skb); - conn->rx_skb = NULL; - conn->rx_len = 0; + l2cap_recv_reset(conn); l2cap_conn_unreliable(conn, ECOMM); goto drop; } - skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len), - skb->len); - conn->rx_len -= skb->len; + /* Append fragment into frame (with header) */ + l2cap_recv_frag(conn, skb, skb->len); if (!conn->rx_len) { /* Complete frame received. l2cap_recv_frame -- 2.26.2
