kernel/linux.git/net/bluetooth/l2cap_core.c, branch v7.0.10

Bluetooth: l2cap: Add missing chan lock in l2cap_ecred_reconf_rsp

2026-05-23T11:08:40+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

2026-05-23T11:08:40+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

2026-03-25T19:32:32+00:00

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

Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

2026-03-25T19:32:09+00:00

l2cap_conn_del() calls cancel_delayed_work_sync() for both info_timer and id_addr_timer while holding conn->lock. However, the work functions l2cap_info_timeout() and l2cap_conn_update_id_addr() both acquire conn->lock, creating a potential AB-BA deadlock if the work is already executing when l2cap_conn_del() takes the lock. Move the work cancellations before acquiring conn->lock and use disable_delayed_work_sync() to additionally prevent the works from being rearmed after cancellation, consistent with the pattern used in hci_conn_del(). Fixes: ab4eedb790ca ("Bluetooth: L2CAP: Fix corrupted list in hci_chan_del") Signed-off-by: Hyunwoo Kim Signed-off-by: Luiz Augusto von Dentz

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

2026-03-25T19:24:02+00:00

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

Bluetooth: L2CAP: Fix regressions caused by reusing ident

2026-03-19T18:44:25+00:00

This attempt to fix regressions caused by reusing ident which apparently is not handled well on certain stacks causing the stack to not respond to requests, so instead of simple returning the first unallocated id this stores the last used tx_ident and then attempt to use the next until all available ids are exausted and then cycle starting over to 1. Link: https://bugzilla.kernel.org/show_bug.cgi?id=221120 Link: https://bugzilla.kernel.org/show_bug.cgi?id=221177 Fixes: 6c3ea155e5ee ("Bluetooth: L2CAP: Fix not tracking outstanding TX ident") Signed-off-by: Luiz Augusto von Dentz Tested-by: Christian Eggers

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

2026-03-19T18:42:12+00:00

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

Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req

2026-03-19T18:38:07+00:00

Syzbot reported a KASAN stack-out-of-bounds read in l2cap_build_cmd() that is triggered by a malformed Enhanced Credit Based Connection Request. The vulnerability stems from l2cap_ecred_conn_req(). The function allocates a local stack buffer (`pdu`) designed to hold a maximum of 5 Source Channel IDs (SCIDs), totaling 18 bytes. When an attacker sends a request with more than 5 SCIDs, the function calculates `rsp_len` based on this unvalidated `cmd_len` before checking if the number of SCIDs exceeds L2CAP_ECRED_MAX_CID. If the SCID count is too high, the function correctly jumps to the `response` label to reject the packet, but `rsp_len` retains the attacker's oversized value. Consequently, l2cap_send_cmd() is instructed to read past the end of the 18-byte `pdu` buffer, triggering a KASAN panic. Fix this by moving the assignment of `rsp_len` to after the `num_scid` boundary check. If the packet is rejected, `rsp_len` will safely remain 0, and the error response will only read the 8-byte base header from the stack. Fixes: c28d2bff7044 ("Bluetooth: L2CAP: Fix result of L2CAP_ECRED_CONN_RSP when MTU is too short") Reported-by: syzbot+b7f3e7d9a596bf6a63e3@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b7f3e7d9a596bf6a63e3 Tested-by: syzbot+b7f3e7d9a596bf6a63e3@syzkaller.appspotmail.com Signed-off-by: Minseo Park Signed-off-by: Luiz Augusto von Dentz

Bluetooth: L2CAP: Validate L2CAP_INFO_RSP payload length before access

2026-03-12T19:29:07+00:00

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

Bluetooth: L2CAP: Fix type confusion in l2cap_ecred_reconf_rsp()

2026-03-12T19:28:46+00:00

l2cap_ecred_reconf_rsp() casts the incoming data to struct l2cap_ecred_conn_rsp (the ECRED *connection* response, 8 bytes with result at offset 6) instead of struct l2cap_ecred_reconf_rsp (2 bytes with result at offset 0). This causes two problems: - The sizeof(*rsp) length check requires 8 bytes instead of the correct 2, so valid L2CAP_ECRED_RECONF_RSP packets are rejected with -EPROTO. - rsp->result reads from offset 6 instead of offset 0, returning wrong data when the packet is large enough to pass the check. Fix by using the correct type. Also pass the already byte-swapped result variable to BT_DBG instead of the raw __le16 field. Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Cc: stable@vger.kernel.org Signed-off-by: Lukas Johannes Möller Signed-off-by: Luiz Augusto von Dentz