kernel.git/net/bluetooth/l2cap_core.c, branch linux-rolling-stable

Bluetooth: L2CAP: Fix missing key size check for L2CAP_LE_CONN_REQ

2026-03-04T12:20:47Z

[ Upstream commit 138d7eca445ef37a0333425d269ee59900ca1104 ] This adds a check for encryption key size upon receiving L2CAP_LE_CONN_REQ which is required by L2CAP/LE/CFC/BV-15-C which expects L2CAP_CR_LE_BAD_KEY_SIZE. Link: https://lore.kernel.org/linux-bluetooth/5782243.rdbgypaU67@n9w6sw14/ Fixes: 27e2d4c8d28b ("Bluetooth: Add basic LE L2CAP connect request receiving support") Signed-off-by: Luiz Augusto von Dentz Tested-by: Christian Eggers Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Fix not checking output MTU is acceptable on L2CAP_ECRED_CONN_REQ

2026-03-04T12:20:47Z

[ Upstream commit a8d1d73c81d1e70d2aa49fdaf59d933bb783ffe5 ] Upon receiving L2CAP_ECRED_CONN_REQ the given MTU shall be checked against the suggested MTU of the listening socket as that is required by the likes of PTS L2CAP/ECFC/BV-27-C test which expects L2CAP_CR_LE_UNACCEPT_PARAMS if the MTU is lowers than socket omtu. In order to be able to set chan->omtu the code now allows setting setsockopt(BT_SNDMTU), but it is only allowed when connection has not been stablished since there is no procedure to reconfigure the output MTU. Link: https://github.com/bluez/bluez/issues/1895 Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Fix response to L2CAP_ECRED_CONN_REQ

2026-03-04T12:20:47Z

[ Upstream commit 05761c2c2b5bfec85c47f60c903c461e9b56cf87 ] Similar to 03dba9cea72f ("Bluetooth: L2CAP: Fix not responding with L2CAP_CR_LE_ENCRYPTION") the result code L2CAP_CR_LE_ENCRYPTION shall be used when BT_SECURITY_MEDIUM is set since that means security mode 2 which mean it doesn't require authentication which results in qualification test L2CAP/ECFC/BV-32-C failing. Link: https://github.com/bluez/bluez/issues/1871 Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Fix result of L2CAP_ECRED_CONN_RSP when MTU is too short

2026-03-04T12:20:47Z

[ Upstream commit c28d2bff70444a85b3b86aaf241ece9408c7858c ] Test L2CAP/ECFC/BV-26-C expect the response to L2CAP_ECRED_CONN_REQ with and MTU value < L2CAP_ECRED_MIN_MTU (64) to be L2CAP_CR_LE_INVALID_PARAMS rather than L2CAP_CR_LE_UNACCEPT_PARAMS. Also fix not including the correct number of CIDs in the response since the spec requires all CIDs being rejected to be included in the response. Link: https://github.com/bluez/bluez/issues/1868 Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: L2CAP: Fix invalid response to L2CAP_ECRED_RECONF_REQ

2026-03-04T12:20:47Z

[ Upstream commit 7accb1c4321acb617faf934af59d928b0b047e2b ] This fixes responding with an invalid result caused by checking the wrong size of CID which should have been (cmd_len - sizeof(*req)) and on top of it the wrong result was use L2CAP_CR_LE_INVALID_PARAMS which is invalid/reserved for reconf when running test like L2CAP/ECFC/BI-03-C: > ACL Data RX: Handle 64 flags 0x02 dlen 14 LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 2 len 6 MTU: 64 MPS: 64 Source CID: 64 < ACL Data TX: Handle 64 flags 0x00 dlen 10 LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2 ! Result: Reserved (0x000c) Result: Reconfiguration failed - one or more Destination CIDs invalid (0x0003) Fiix L2CAP/ECFC/BI-04-C which expects L2CAP_RECONF_INVALID_MPS (0x0002) when more than one channel gets its MPS reduced: > ACL Data RX: Handle 64 flags 0x02 dlen 16 LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 2 len 8 MTU: 264 MPS: 99 Source CID: 64 ! Source CID: 65 < ACL Data TX: Handle 64 flags 0x00 dlen 10 LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2 ! Result: Reconfiguration successful (0x0000) Result: Reconfiguration failed - reduction in size of MPS not allowed for more than one channel at a time (0x0002) Fix L2CAP/ECFC/BI-05-C when SCID is invalid (85 unconnected): > ACL Data RX: Handle 64 flags 0x02 dlen 14 LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 2 len 6 MTU: 65 MPS: 64 ! Source CID: 85 < ACL Data TX: Handle 64 flags 0x00 dlen 10 LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2 ! Result: Reconfiguration successful (0x0000) Result: Reconfiguration failed - one or more Destination CIDs invalid (0x0003) Fix L2CAP/ECFC/BI-06-C when MPS < L2CAP_ECRED_MIN_MPS (64): > ACL Data RX: Handle 64 flags 0x02 dlen 14 LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 2 len 6 MTU: 672 ! MPS: 63 Source CID: 64 < ACL Data TX: Handle 64 flags 0x00 dlen 10 LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2 ! Result: Reconfiguration failed - reduction in size of MPS not allowed for more than one channel at a time (0x0002) Result: Reconfiguration failed - other unacceptable parameters (0x0004) Fix L2CAP/ECFC/BI-07-C when MPS reduced for more than one channel: > ACL Data RX: Handle 64 flags 0x02 dlen 16 LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 3 len 8 MTU: 84 ! MPS: 71 Source CID: 64 ! Source CID: 65 < ACL Data TX: Handle 64 flags 0x00 dlen 10 LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2 ! Result: Reconfiguration successful (0x0000) Result: Reconfiguration failed - reduction in size of MPS not allowed for more than one channel at a time (0x0002) Link: https://github.com/bluez/bluez/issues/1865 Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin

Bluetooth: hci_core: lookup hci_conn on RX path on protocol side

2025-11-20T22:01:09Z

The hdev lock/lookup/unlock/use pattern in the packet RX path doesn't ensure hci_conn* is not concurrently modified/deleted. This locking appears to be leftover from before conn_hash started using RCU commit bf4c63252490b ("Bluetooth: convert conn hash to RCU") and not clear if it had purpose since then. Currently, there are code paths that delete hci_conn* from elsewhere than the ordered hdev->workqueue where the RX work runs in. E.g. commit 5af1f84ed13a ("Bluetooth: hci_sync: Fix UAF on hci_abort_conn_sync") introduced some of these, and there probably were a few others before it. It's better to do the locking so that even if these run concurrently no UAF is possible. Move the lookup of hci_conn and associated socket-specific conn to protocol recv handlers, and do them within a single critical section to cover hci_conn* usage and lookup. syzkaller has reported a crash that appears to be this issue: [Task hdev->workqueue] [Task 2] hci_disconnect_all_sync l2cap_recv_acldata(hcon) hci_conn_get(hcon) hci_abort_conn_sync(hcon) hci_dev_lock hci_dev_lock hci_conn_del(hcon) v-------------------------------- hci_dev_unlock hci_conn_put(hcon) conn = hcon->l2cap_data (UAF) Fixes: 5af1f84ed13a ("Bluetooth: hci_sync: Fix UAF on hci_abort_conn_sync") Reported-by: syzbot+d32d77220b92eddd89ad@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d32d77220b92eddd89ad Signed-off-by: Pauli Virtanen Signed-off-by: Luiz Augusto von Dentz

Bluetooth: L2CAP: export l2cap_chan_hold for modules

2025-11-10T21:08:00Z

l2cap_chan_put() is exported, so export also l2cap_chan_hold() for modules. l2cap_chan_hold() has use case in net/bluetooth/6lowpan.c Signed-off-by: Pauli Virtanen Reviewed-by: Paul Menzel Signed-off-by: Luiz Augusto von Dentz

Revert "Bluetooth: L2CAP: convert timeouts to secs_to_jiffies()"

2025-10-24T14:30:30Z

This reverts commit c9d84da18d1e0d28a7e16ca6df8e6d47570501d4. It replaces in L2CAP calls to msecs_to_jiffies() to secs_to_jiffies() and updates the constants accordingly. But the constants are also used in LCAP Configure Request and L2CAP Configure Response which expect values in milliseconds. This may prevent correct usage of L2CAP channel. To fix it, keep those constants in milliseconds and so revert this change. Fixes: c9d84da18d1e ("Bluetooth: L2CAP: convert timeouts to secs_to_jiffies()") Signed-off-by: Frédéric Danis Signed-off-by: Luiz Augusto von Dentz

Bluetooth: L2CAP: Fix attempting to adjust outgoing MTU

2025-07-17T14:26:53Z

Configuration request only configure the incoming direction of the peer initiating the request, so using the MTU is the other direction shall not be used, that said the spec allows the peer responding to adjust: Bluetooth Core 6.1, Vol 3, Part A, Section 4.5 'Each configuration parameter value (if any is present) in an L2CAP_CONFIGURATION_RSP packet reflects an ‘adjustment’ to a configuration parameter value that has been sent (or, in case of default values, implied) in the corresponding L2CAP_CONFIGURATION_REQ packet.' That said adjusting the MTU in the response shall be limited to ERTM channels only as for older modes the remote stack may not be able to detect the adjustment causing it to silently drop packets. Link: https://github.com/bluez/bluez/issues/1422 Link: https://gitlab.archlinux.org/archlinux/packaging/packages/linux/-/issues/149 Link: https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/4793 Fixes: 042bb9603c44 ("Bluetooth: L2CAP: Fix L2CAP MTU negotiation") Signed-off-by: Luiz Augusto von Dentz

Bluetooth: L2CAP: Fix L2CAP MTU negotiation

2025-06-20T15:54:48Z

OBEX download from iPhone is currently slow due to small packet size used to transfer data which doesn't follow the MTU negotiated during L2CAP connection, i.e. 672 bytes instead of 32767: < ACL Data TX: Handle 11 flags 0x00 dlen 12 L2CAP: Connection Request (0x02) ident 18 len 4 PSM: 4103 (0x1007) Source CID: 72 > ACL Data RX: Handle 11 flags 0x02 dlen 16 L2CAP: Connection Response (0x03) ident 18 len 8 Destination CID: 14608 Source CID: 72 Result: Connection successful (0x0000) Status: No further information available (0x0000) < ACL Data TX: Handle 11 flags 0x00 dlen 27 L2CAP: Configure Request (0x04) ident 20 len 19 Destination CID: 14608 Flags: 0x0000 Option: Maximum Transmission Unit (0x01) [mandatory] MTU: 32767 Option: Retransmission and Flow Control (0x04) [mandatory] Mode: Enhanced Retransmission (0x03) TX window size: 63 Max transmit: 3 Retransmission timeout: 2000 Monitor timeout: 12000 Maximum PDU size: 1009 > ACL Data RX: Handle 11 flags 0x02 dlen 26 L2CAP: Configure Request (0x04) ident 72 len 18 Destination CID: 72 Flags: 0x0000 Option: Retransmission and Flow Control (0x04) [mandatory] Mode: Enhanced Retransmission (0x03) TX window size: 32 Max transmit: 255 Retransmission timeout: 0 Monitor timeout: 0 Maximum PDU size: 65527 Option: Frame Check Sequence (0x05) [mandatory] FCS: 16-bit FCS (0x01) < ACL Data TX: Handle 11 flags 0x00 dlen 29 L2CAP: Configure Response (0x05) ident 72 len 21 Source CID: 14608 Flags: 0x0000 Result: Success (0x0000) Option: Maximum Transmission Unit (0x01) [mandatory] MTU: 672 Option: Retransmission and Flow Control (0x04) [mandatory] Mode: Enhanced Retransmission (0x03) TX window size: 32 Max transmit: 255 Retransmission timeout: 2000 Monitor timeout: 12000 Maximum PDU size: 1009 > ACL Data RX: Handle 11 flags 0x02 dlen 32 L2CAP: Configure Response (0x05) ident 20 len 24 Source CID: 72 Flags: 0x0000 Result: Success (0x0000) Option: Maximum Transmission Unit (0x01) [mandatory] MTU: 32767 Option: Retransmission and Flow Control (0x04) [mandatory] Mode: Enhanced Retransmission (0x03) TX window size: 63 Max transmit: 3 Retransmission timeout: 2000 Monitor timeout: 12000 Maximum PDU size: 1009 Option: Frame Check Sequence (0x05) [mandatory] FCS: 16-bit FCS (0x01) ... > ACL Data RX: Handle 11 flags 0x02 dlen 680 Channel: 72 len 676 ctrl 0x0202 [PSM 4103 mode Enhanced Retransmission (0x03)] {chan 8} I-frame: Unsegmented TxSeq 1 ReqSeq 2 < ACL Data TX: Handle 11 flags 0x00 dlen 13 Channel: 14608 len 9 ctrl 0x0204 [PSM 4103 mode Enhanced Retransmission (0x03)] {chan 8} I-frame: Unsegmented TxSeq 2 ReqSeq 2 > ACL Data RX: Handle 11 flags 0x02 dlen 680 Channel: 72 len 676 ctrl 0x0304 [PSM 4103 mode Enhanced Retransmission (0x03)] {chan 8} I-frame: Unsegmented TxSeq 2 ReqSeq 3 The MTUs are negotiated for each direction. In this traces 32767 for iPhone->localhost and no MTU for localhost->iPhone, which based on '4.4 L2CAP_CONFIGURATION_REQ' (Core specification v5.4, Vol. 3, Part A): The only parameters that should be included in the L2CAP_CONFIGURATION_REQ packet are those that require different values than the default or previously agreed values. ... Any missing configuration parameters are assumed to have their most recently explicitly or implicitly accepted values. and '5.1 Maximum transmission unit (MTU)': If the remote device sends a positive L2CAP_CONFIGURATION_RSP packet it should include the actual MTU to be used on this channel for traffic flowing into the local device. ... The default value is 672 octets. is set by BlueZ to 672 bytes. It seems that the iPhone used the lowest negotiated value to transfer data to the localhost instead of the negotiated one for the incoming direction. This could be fixed by using the MTU negotiated for the other direction, if exists, in the L2CAP_CONFIGURATION_RSP. This allows to use segmented packets as in the following traces: < ACL Data TX: Handle 11 flags 0x00 dlen 12 L2CAP: Connection Request (0x02) ident 22 len 4 PSM: 4103 (0x1007) Source CID: 72 < ACL Data TX: Handle 11 flags 0x00 dlen 27 L2CAP: Configure Request (0x04) ident 24 len 19 Destination CID: 2832 Flags: 0x0000 Option: Maximum Transmission Unit (0x01) [mandatory] MTU: 32767 Option: Retransmission and Flow Control (0x04) [mandatory] Mode: Enhanced Retransmission (0x03) TX window size: 63 Max transmit: 3 Retransmission timeout: 2000 Monitor timeout: 12000 Maximum PDU size: 1009 > ACL Data RX: Handle 11 flags 0x02 dlen 26 L2CAP: Configure Request (0x04) ident 15 len 18 Destination CID: 72 Flags: 0x0000 Option: Retransmission and Flow Control (0x04) [mandatory] Mode: Enhanced Retransmission (0x03) TX window size: 32 Max transmit: 255 Retransmission timeout: 0 Monitor timeout: 0 Maximum PDU size: 65527 Option: Frame Check Sequence (0x05) [mandatory] FCS: 16-bit FCS (0x01) < ACL Data TX: Handle 11 flags 0x00 dlen 29 L2CAP: Configure Response (0x05) ident 15 len 21 Source CID: 2832 Flags: 0x0000 Result: Success (0x0000) Option: Maximum Transmission Unit (0x01) [mandatory] MTU: 32767 Option: Retransmission and Flow Control (0x04) [mandatory] Mode: Enhanced Retransmission (0x03) TX window size: 32 Max transmit: 255 Retransmission timeout: 2000 Monitor timeout: 12000 Maximum PDU size: 1009 > ACL Data RX: Handle 11 flags 0x02 dlen 32 L2CAP: Configure Response (0x05) ident 24 len 24 Source CID: 72 Flags: 0x0000 Result: Success (0x0000) Option: Maximum Transmission Unit (0x01) [mandatory] MTU: 32767 Option: Retransmission and Flow Control (0x04) [mandatory] Mode: Enhanced Retransmission (0x03) TX window size: 63 Max transmit: 3 Retransmission timeout: 2000 Monitor timeout: 12000 Maximum PDU size: 1009 Option: Frame Check Sequence (0x05) [mandatory] FCS: 16-bit FCS (0x01) ... > ACL Data RX: Handle 11 flags 0x02 dlen 1009 Channel: 72 len 1005 ctrl 0x4202 [PSM 4103 mode Enhanced Retransmission (0x03)] {chan 8} I-frame: Start (len 21884) TxSeq 1 ReqSeq 2 > ACL Data RX: Handle 11 flags 0x02 dlen 1009 Channel: 72 len 1005 ctrl 0xc204 [PSM 4103 mode Enhanced Retransmission (0x03)] {chan 8} I-frame: Continuation TxSeq 2 ReqSeq 2 This has been tested with kernel 5.4 and BlueZ 5.77. Cc: stable@vger.kernel.org Signed-off-by: Frédéric Danis Signed-off-by: Luiz Augusto von Dentz