kernel/git/stable/linux.git/net/bluetooth/rfcomm, branch master

Bluetooth: RFCOMM: serialize session teardown

2026-08-24T17:14:43+00:00

rfcomm_kill_listener() walks session_list and deletes every session without holding rfcomm_mutex, unlike the normal session processing and connect error paths. Under normal operation, an open RFCOMM socket pins rfcomm.ko, so rfcomm_kill_listener() does not run concurrently with rfcomm_dlc_open(). However, forced module unload via delete_module(O_TRUNC) can stop krfcommd while a failed connect is still unwinding. connect task forced unload / krfcommd ------------ ------------------------ rfcomm_lock() rfcomm_session_add() delete_module("rfcomm", O_TRUNC) rfcomm_kill_listener() fetch session from session_list kernel_connect() fails rfcomm_session_del() remove and free session rfcomm_session_del(session) The final call then reads the freed session and may corrupt the list. KASAN reported with mdelay() to enlarge critical window: BUG: KASAN: slab-use-after-free in rfcomm_run+0x3802/0x3f00 [rfcomm] Read of size 8 at addr ffff888111058d40 by task krfcommd/79 Tainted: [R]=FORCED_RMMOD Allocated by task 86: rfcomm_session_add+0xa1/0x300 [rfcomm] rfcomm_dlc_open+0x8b2/0xf30 [rfcomm] rfcomm_sock_connect+0x34c/0x530 [rfcomm] Freed by task 86: kfree+0x121/0x3c0 rfcomm_dlc_open+0xab7/0xf30 [rfcomm] rfcomm_sock_connect+0x34c/0x530 [rfcomm] Hold rfcomm_mutex across the teardown traversal so every reachable session_list walk uses the same serialization. Reviewed-by: Ali Ahmet Memis Tested-by: Ali Ahmet Memis Reviewed-by: Pauli Virtanen Signed-off-by: Chengfeng Ye Signed-off-by: Luiz Augusto von Dentz

Bluetooth: RFCOMM: serialize security confirmation handling

2026-08-24T17:13:36+00:00

rfcomm_security_cfm() looks up a session on session_list and then walks its DLC list without holding rfcomm_mutex. Since RFCOMM session teardown uses rfcomm_mutex, krfcommd can close and free the same session and DLCs concurrently: hci_rx_work krfcommd ----------- --------- rfcomm_session_get() rfcomm_lock() rfcomm_session_close() rfcomm_dlc_unlink() rfcomm_session_del() kfree(s) rfcomm_unlock() walk s->dlcs The callback can then read a freed session list head and touch freed DLCs while updating their flags or timers. Serialize the session lookup and DLC traversal in rfcomm_security_cfm() with rfcomm_mutex. This matches the existing RFCOMM session lifetime rules and prevents concurrent rfcomm_session_del() / rfcomm_dlc_unlink() from tearing the objects down while the callback is using them. KASAN reported: BUG: KASAN: slab-use-after-free in rfcomm_security_cfm+0x41c/0x440 Read of size 8 at addr ffff888111fb3960 by task kworker/u17:1/89 Workqueue: hci0 hci_rx_work Call Trace: rfcomm_security_cfm+0x41c/0x440 hci_encrypt_cfm+0x139/0x590 hci_encrypt_change_evt+0x37b/0xc40 hci_event_packet+0x71b/0xb20 hci_rx_work+0x293/0x730 Allocated by task 69: rfcomm_session_add+0x9e/0x2f0 rfcomm_run+0x44b/0x41e0 Freed by task 69: kfree+0x131/0x3c0 rfcomm_session_del+0x188/0x220 rfcomm_run+0x1985/0x41e0 Fixes: 08c30aca9e698faddebd34f81e1196295f9dc063 ("Bluetooth: Remove RFCOMM session refcnt") Cc: stable@vger.kernel.org Signed-off-by: Chengfeng Ye Signed-off-by: Luiz Augusto von Dentz

Bluetooth: RFCOMM: Validate MTU in rfcomm_apply_pn() to prevent infinite loop

2026-08-24T17:13:13+00:00

rfcomm_apply_pn() accepts the MTU value from a remote PN (Parameter Negotiation) frame without checking for zero. When the remote peer sends an MTU of zero, d->mtu is set to 0. This causes the sendmsg path to enter an infinite loop when fragmenting data, as each fragment has size == min_t(size_t, len, 0) == 0, so the remaining length never decreases. The infinite allocation of zero-length skbs exhausts all system memory. Fix by clamping d->mtu to RFCOMM_DEFAULT_MTU when the negotiated value is zero, consistent with the initial value assigned in rfcomm_dlc_alloc(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Hyunwoo Kim Signed-off-by: Luiz Augusto von Dentz

Bluetooth: RFCOMM: take rfcomm_mutex for the deferred setup accept

2026-08-07T19:40:28+00:00

rfcomm_sock_recvmsg() completes a deferred setup by calling rfcomm_dlc_accept() without holding any RFCOMM lock: if (test_and_clear_bit(RFCOMM_DEFER_SETUP, &d->flags)) { rfcomm_dlc_accept(d); return 0; } and rfcomm_dlc_accept() dereferences the session on its first line: struct sock *sk = d->session->sock->sk; Every other path that touches d->session runs under rfcomm_mutex: rfcomm_dlc_open(), rfcomm_dlc_close(), rfcomm_dlc_exists(), rfcomm_dlc_send_rpn(), and the RFCOMM thread through rfcomm_process_sessions(). rfcomm_connect_ind() is even documented as "called under rfcomm_lock()". This call site is the only one that skips it. The RFCOMM_DEFER_SETUP bit looks like it serialises the accept against teardown, since __rfcomm_dlc_close() returns early when it wins the test_and_clear. But rfcomm_recv_disc() forces the state first: d->state = BT_CLOSED; __rfcomm_dlc_close(d, err); and the early return only covers BT_CONNECT, BT_CONFIG, BT_OPEN and BT_CONNECT2. With the state already BT_CLOSED that switch does not match, the bit is never consulted, and __rfcomm_dlc_close() falls through to rfcomm_dlc_unlink(), which sets d->session = NULL. So a remote DISC on a deferred dlc clears the session while leaving RFCOMM_DEFER_SETUP set. The next recvmsg() then passes the test_and_clear and dereferences a NULL session. No timing window is needed: once the DISC has been processed, the dereference is unconditional. Give rfcomm_dlc_accept() the same shape as rfcomm_dlc_open() and rfcomm_dlc_close(): an exported wrapper that takes rfcomm_mutex and re-checks the session, around a __rfcomm_dlc_accept() that the two in-core callers, which already hold the mutex, keep using. Reproduced on a KASAN + PROVE_LOCKING kernel with a BR/EDR peer emulated over /dev/vhci: the peer brings up an ACL link, opens L2CAP on the RFCOMM PSM, starts a session, opens a dlc on a channel bound with BT_DEFER_SETUP, and sends DISC after the socket is accepted. recv() on the accepted socket then hits: Oops: general protection fault KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:rfcomm_dlc_accept+0x54/0x350 Call Trace: rfcomm_sock_recvmsg+0x1cd/0x230 sock_recvmsg+0x166/0x1c0 __sys_recvfrom+0x20d/0x300 0x10 is the offset of sock in struct rfcomm_session. With this patch the same run completes with recv() returning 0 and no report, and lockdep stays quiet, confirming rfcomm_mutex is still taken before lock_sock on this path as it is on the thread side. Fixes: bb23c0ab8246 ("Bluetooth: Add support for deferring RFCOMM connection setup") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Luiz Augusto von Dentz

Bluetooth: fix BT dependency for submodules

2026-08-07T19:38:30+00:00

The modules rfcomm (BT_RFCOMM), bnep (BT_BNEP), hidp (BT_HIDP), and bluetooth_6lowpan (BT_6LOWPAN) are dependent on the bluetooth module (BT, tristate) only transitively through the boolean BT_BREDR for the first three and through the boolean BT_LE for the bluetooth_6lowpan. Therefore, the modules can be selected as built-in even if the BT=m. The combination of BT=m and =y for the said modules leads to the kernel build system silently ignoring those modules, without ever compiling them as built-in or as loadable modules. Add BT as a direct dependency to the Kconfig of rfcomm, bnep, hidp, and bluetooth_6lowpan. The modules set to =y when BT=m will default to =m, rather then getting silently ignored by the build system. Signed-off-by: Iva Kasprzaková Signed-off-by: Luiz Augusto von Dentz

Bluetooth: enable context analysis

2026-08-07T16:27:20+00:00

Enable compiler context analysis for Bluetooth subsystem and drivers. Signed-off-by: Pauli Virtanen Signed-off-by: Luiz Augusto von Dentz

Bluetooth: RFCOMM: Add minimal context analysis annotations

2026-08-07T16:27:02+00:00

Add minimal compiler context analysis annotations, required for compilation to pass. Signed-off-by: Pauli Virtanen Signed-off-by: Luiz Augusto von Dentz

Bluetooth: RFCOMM: validate skb length in rfcomm_recv_frame

2026-07-28T19:01:31+00:00

rfcomm_recv_frame() casts skb->data to struct rfcomm_hdr and dereferences hdr->addr and hdr->ctrl without validating skb->len first. A truncated frame with skb->len less than the minimum header size causes an out-of-bounds read of uninitialized memory. Additionally, a zero-length frame causes skb->len-- to underflow to UINT_MAX, making skb_tail_pointer() read far past the buffer. Commit 23882b828c3c ("Bluetooth: RFCOMM: validate skb length in MCC handlers") fixed the same class of missing-length-check bugs in the MCC sub-handlers, but the top-level rfcomm_recv_frame() was left unfixed. KMSAN reports: BUG: KMSAN: uninit-value in rfcomm_run ... Uninit was created at: __alloc_skb+0x474/0xb60 vhci_write+0xe9/0x870 Fix this by rejecting frames smaller than sizeof(struct rfcomm_hdr) + 1 (the minimum frame must have a 3-byte header and a 1-byte FCS). Signed-off-by: Jiale Yao Signed-off-by: Luiz Augusto von Dentz

Bluetooth: RFCOMM: Fix session UAF in set_termios

2026-07-20T21:41:07+00:00

rfcomm_tty_set_termios() tests dlc->session without rfcomm_mutex and later passes the pointer to rfcomm_send_rpn(). The latter dereferences both session->initiator and session->sock. Meanwhile, krfcommd can unlink the DLC and free the session while holding rfcomm_mutex. The race can proceed as follows: TTY ioctl task krfcommd -------------- -------- load dlc->session enter rfcomm_send_rpn() lock rfcomm_mutex clear dlc->session free session unlock rfcomm_mutex read session->initiator KASAN reported: BUG: KASAN: slab-use-after-free in rfcomm_send_rpn+0x297/0x2a0 Read of size 4 at addr ffff88810012a850 by task poc/92 Call Trace: rfcomm_send_rpn+0x297/0x2a0 rfcomm_tty_set_termios+0x50d/0x850 tty_set_termios+0x596/0x950 set_termios+0x46a/0x6e0 tty_mode_ioctl+0x152/0xbd0 tty_ioctl+0x915/0x1240 __x64_sys_ioctl+0x134/0x1c0 Allocated by task 92: rfcomm_session_add+0x9e/0x2e0 rfcomm_dlc_open+0x8b1/0xe00 rfcomm_dev_activate+0x85/0x1a0 rfcomm_tty_open+0x90/0x280 Freed by task 68: kfree+0x131/0x3c0 rfcomm_session_del+0x119/0x180 rfcomm_run+0x737/0x4710 Add rfcomm_dlc_send_rpn(), which holds rfcomm_mutex while it verifies that the DLC is still attached and sends the RPN frame. Have the TTY path use the helper and drop its unlocked session check. This keeps the session valid through both the frame construction and socket send. Fixes: 3a5e903c09ae ("[Bluetooth]: Implement RFCOMM remote port negotiation") Cc: stable@vger.kernel.org Signed-off-by: Chengfeng Ye Signed-off-by: Luiz Augusto von Dentz

Bluetooth: Add SPDX id lines to some source files

2026-06-11T18:24:41+00:00

Many bluetooth source files are missing SPDX-License-Identifier lines. Add appropriate IDs to these files, and remove other license lines from the headers. Leave the warranty disclaimer in files where the license ID is GPL-2.0 but the wording of the disclaimer is slightly different from that of the GPL v2 disclaimer. It is not different enough to cause licensing conflicts, but is kept to honor the original contributors' legal intent. Signed-off-by: Tim Bird Signed-off-by: Luiz Augusto von Dentz