kernel/linux.git/net/bluetooth/l2cap_core.c, branch v6.6.141

Bluetooth: l2cap: Add missing chan lock in l2cap_ecred_reconf_rsp

2026-05-23T11:03:09+00:00

[ Upstream commit 42776497cdbc9a665b384a6dcb85f0d4bd927eab ] l2cap_ecred_reconf_rsp() calls l2cap_chan_del() without holding l2cap_chan_lock(). Every other l2cap_chan_del() caller in the file acquires the lock first. A remote BLE device can send a crafted L2CAP ECRED reconfiguration response to corrupt the channel list while another thread is iterating it. Add l2cap_chan_hold() and l2cap_chan_lock() before l2cap_chan_del(), and l2cap_chan_unlock() and l2cap_chan_put() after, matching the pattern used in l2cap_ecred_conn_rsp() and l2cap_conn_del(). Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Signed-off-by: Dudu Lu Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Fix printing wrong information if SDU length exceeds MTU

2026-05-23T11:03:09+00:00

[ Upstream commit 15bf35a660eb82a49f8397fc3d3acada8dae13db ] The code was printing skb->len and sdu_len in the places where it should be sdu_len and chan->imtu respectively to match the if conditions. Link: https://lore.kernel.org/linux-bluetooth/20260315132013.75ab40c5@kernel.org/T/#m1418f9c82eeff8510c1beaa21cf53af20db96c06 Fixes: e1d9a6688986 ("Bluetooth: LE L2CAP: Disconnect if received packet's SDU exceeds IMTU") Signed-off-by: Luiz Augusto von Dentz Reviewed-by: Paul Menzel Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Fix ERTM re-init and zero pdu_len infinite loop

2026-04-02T11:07:20+00:00

[ Upstream commit 25f420a0d4cfd61d3d23ec4b9c56d9f443d91377 ] l2cap_config_req() processes CONFIG_REQ for channels in BT_CONNECTED state to support L2CAP reconfiguration (e.g. MTU changes). However, since both CONF_INPUT_DONE and CONF_OUTPUT_DONE are already set from the initial configuration, the reconfiguration path falls through to l2cap_ertm_init(), which re-initializes tx_q, srej_q, srej_list, and retrans_list without freeing the previous allocations and sets chan->sdu to NULL without freeing the existing skb. This leaks all previously allocated ERTM resources. Additionally, l2cap_parse_conf_req() does not validate the minimum value of remote_mps derived from the RFC max_pdu_size option. A zero value propagates to l2cap_segment_sdu() where pdu_len becomes zero, causing the while loop to never terminate since len is never decremented, exhausting all available memory. Fix the double-init by skipping l2cap_ertm_init() and l2cap_chan_ready() when the channel is already in BT_CONNECTED state, while still allowing the reconfiguration parameters to be updated through l2cap_parse_conf_req(). Also add a pdu_len zero check in l2cap_segment_sdu() as a safeguard. Fixes: 96298f640104 ("Bluetooth: L2CAP: handle l2cap config request during open state") Signed-off-by: Hyunwoo Kim Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Fix send LE flow credits in ACL link

2026-04-02T11:07:19+00:00

[ Upstream commit f39f905e55f529b036321220af1ba4f4085564a5 ] When the L2CAP channel mode is L2CAP_MODE_ERTM/L2CAP_MODE_STREAMING, l2cap_publish_rx_avail will be called and le flow credits will be sent in l2cap_chan_rx_avail, even though the link type is ACL. The logs in question as follows: > ACL Data RX: Handle 129 flags 0x02 dlen 12 L2CAP: Unknown (0x16) ident 4 len 4 40 00 ed 05 < ACL Data TX: Handle 129 flags 0x00 dlen 10 L2CAP: Command Reject (0x01) ident 4 len 2 Reason: Command not understood (0x0000) Bluetooth: Unknown BR/EDR signaling command 0x16 Bluetooth: Wrong link type (-22) Fixes: ce60b9231b66 ("Bluetooth: compute LE flow credits based on recvbuf space") Signed-off-by: Zhang Chen Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Validate PDU length before reading SDU length in l2cap_ecred_data_rcv()

2026-04-02T11:07:16+00:00

[ Upstream commit c65bd945d1c08c3db756821b6bf9f1c4a77b29c6 ] l2cap_ecred_data_rcv() reads the SDU length field from skb->data using get_unaligned_le16() without first verifying that skb contains at least L2CAP_SDULEN_SIZE (2) bytes. When skb->len is less than 2, this reads past the valid data in the skb. The ERTM reassembly path correctly calls pskb_may_pull() before reading the SDU length (l2cap_reassemble_sdu, L2CAP_SAR_START case). Apply the same validation to the Enhanced Credit Based Flow Control data path. Fixes: aac23bf63659 ("Bluetooth: Implement LE L2CAP reassembly") Signed-off-by: Hyunwoo Kim Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Fix accepting multiple L2CAP_ECRED_CONN_REQ

2026-03-25T10:06:09+00:00

commit 5b3e2052334f2ff6d5200e952f4aa66994d09899 upstream. Currently the code attempts to accept requests regardless of the command identifier which may cause multiple requests to be marked as pending (FLAG_DEFER_SETUP) which can cause more than L2CAP_ECRED_MAX_CID(5) to be allocated in l2cap_ecred_rsp_defer causing an overflow. The spec is quite clear that the same identifier shall not be used on subsequent requests: 'Within each signaling channel a different Identifier shall be used for each successive request or indication.' https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-62/out/en/host/logical-link-control-and-adaptation-protocol-specification.html#UUID-32a25a06-4aa4-c6c7-77c5-dcfe3682355d So this attempts to check if there are any channels pending with the same identifier and rejects if any are found. Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Reported-by: Yiming Qian Signed-off-by: Luiz Augusto von Dentz [ adapted variable names ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

Bluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user

2026-03-25T10:06:06+00:00

[ Upstream commit 752a6c9596dd25efd6978a73ff21f3b592668f4a ] After commit ab4eedb790ca ("Bluetooth: L2CAP: Fix corrupted list in hci_chan_del"), l2cap_conn_del() uses conn->lock to protect access to conn->users. However, l2cap_register_user() and l2cap_unregister_user() don't use conn->lock, creating a race condition where these functions can access conn->users and conn->hchan concurrently with l2cap_conn_del(). This can lead to use-after-free and list corruption bugs, as reported by syzbot. Fix this by changing l2cap_register_user() and l2cap_unregister_user() to use conn->lock instead of hci_dev_lock(), ensuring consistent locking for the l2cap_conn structure. Reported-by: syzbot+14b6d57fb728e27ce23c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=14b6d57fb728e27ce23c Fixes: ab4eedb790ca ("Bluetooth: L2CAP: Fix corrupted list in hci_chan_del") Signed-off-by: Shaurya Rane Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: LE L2CAP: Disconnect if sum of payload sizes exceed SDU

2026-03-25T10:06:06+00:00

[ Upstream commit b6a2bf43aa37670432843bc73ae2a6288ba4d6f8 ] Core 6.0, Vol 3, Part A, 3.4.3: "... If the sum of the payload sizes for the K-frames exceeds the specified SDU length, the receiver shall disconnect the channel." This fixes L2CAP/LE/CFC/BV-27-C (running together with 'l2test -r -P 0x0027 -V le_public'). Fixes: aac23bf63659 ("Bluetooth: Implement LE L2CAP reassembly") Signed-off-by: Christian Eggers Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: LE L2CAP: Disconnect if received packet's SDU exceeds IMTU

2026-03-25T10:06:05+00:00

[ Upstream commit e1d9a66889867c232657a9b6f25d451d7c3ab96f ] Core 6.0, Vol 3, Part A, 3.4.3: "If the SDU length field value exceeds the receiver's MTU, the receiver shall disconnect the channel..." This fixes L2CAP/LE/CFC/BV-26-C (running together with 'l2test -r -P 0x0027 -V le_public -I 100'). Fixes: aac23bf63659 ("Bluetooth: Implement LE L2CAP reassembly") Signed-off-by: Christian Eggers Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Validate L2CAP_INFO_RSP payload length before access

2026-03-25T10:06:02+00:00

commit dd815e6e3918dc75a49aaabac36e4f024d675101 upstream. l2cap_information_rsp() checks that cmd_len covers the fixed l2cap_info_rsp header (type + result, 4 bytes) but then reads rsp->data without verifying that the payload is present: - L2CAP_IT_FEAT_MASK calls get_unaligned_le32(rsp->data), which reads 4 bytes past the header (needs cmd_len >= 8). - L2CAP_IT_FIXED_CHAN reads rsp->data[0], 1 byte past the header (needs cmd_len >= 5). A truncated L2CAP_INFO_RSP with result == L2CAP_IR_SUCCESS triggers an out-of-bounds read of adjacent skb data. Guard each data access with the required payload length check. If the payload is too short, skip the read and let the state machine complete with safe defaults (feat_mask and remote_fixed_chan remain zero from kzalloc), so the info timer cleanup and l2cap_conn_start() still run and the connection is not stalled. Fixes: 4e8402a3f884 ("[Bluetooth] Retrieve L2CAP features mask on connection setup") Cc: stable@vger.kernel.org Signed-off-by: Lukas Johannes Möller Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Greg Kroah-Hartman