kernel/linux.git/drivers/usb/gadget/function/f_ncm.c, branch v6.6.150

usb: gadget: f_ncm: validate datagram bounds in ncm_unwrap_ntb()

2026-08-03T09:15:16+00:00

commit 1febec7e47cdcd01f43fb0211094e3010474666e upstream. When unpacking host-supplied NTBs, ncm_unwrap_ntb() checks datagram length against frame_max but does not verify that the datagram fits within the declared block length. Additionally, when decoding multiple NTBs from a single socket buffer, subsequent block lengths are not checked against the actual remaining buffer data. With these checks missing, a malicious USB host can specify datagram offsets and lengths that point beyond the block, or supply secondary NTB headers declaring lengths larger than the buffer. skb_put_data() then copies adjacent kernel memory from skb_shared_info into the network skb. Fix this by verifying that sufficient buffer space remains for the NTB header before parsing, handling zero-length block declarations, ensuring that block lengths never exceed the remaining buffer space, and verifying that each datagram payload stays strictly within the block boundary. Fixes: 427694cfaafa ("usb: gadget: ncm: Handle decoding of multiple NTB's in unwrap call") Fixes: 2b74b0a04d3e ("USB: gadget: f_ncm: add bounds checks to ncm_unwrap_ntb()") Cc: stable Assisted-by: Jetski:Gemini-2.5-Pro Signed-off-by: Sonali Pradhan Link: https://patch.msgid.link/20260703083725.1903850-1-sonalipradhan@google.com Signed-off-by: Greg Kroah-Hartman

usb: gadget: f_ncm: Fix net_device lifecycle with device_move

2026-06-19T11:39:28+00:00

[ Upstream commit ec35c1969650e7cb6c8a91020e568ed46e3551b0 ] The network device outlived its parent gadget device during disconnection, resulting in dangling sysfs links and null pointer dereference problems. A prior attempt to solve this by removing SET_NETDEV_DEV entirely [1] was reverted due to power management ordering concerns and a NO-CARRIER regression. A subsequent attempt to defer net_device allocation to bind [2] broke 1:1 mapping between function instance and network device, making it impossible for configfs to report the resolved interface name. This results in a regression where the DHCP server fails on pmOS. Use device_move to reparent the net_device between the gadget device and /sys/devices/virtual/ across bind/unbind cycles. This preserves the network interface across USB reconnection, allowing the DHCP server to retain their binding. Introduce gether_attach_gadget()/gether_detach_gadget() helpers and use __free(detach_gadget) macro to undo attachment on bind failure. The bind_count ensures device_move executes only on the first bind. [1] https://lore.kernel.org/lkml/f2a4f9847617a0929d62025748384092e5f35cce.camel@crapouillou.net/ [2] https://lore.kernel.org/linux-usb/795ea759-7eaf-4f78-81f4-01ffbf2d7961@ixit.cz/ Fixes: 40d133d7f542 ("usb: gadget: f_ncm: convert to new function interface with backward compatibility") Cc: stable Signed-off-by: Kuen-Han Tsai Link: https://patch.msgid.link/20260309-f-ncm-revert-v2-7-ea2afbc7d9b2@google.com Signed-off-by: Greg Kroah-Hartman [ Use no_free_ptr() since retain_and_null_ptr() is unavailable in Linux 6.6. ] Signed-off-by: Jianqiang kang Signed-off-by: Carlos Llamas Signed-off-by: Sasha Levin

usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()

2026-04-27T13:23:30+00:00

commit 8f993d30b95dc9557a8a96ceca11abed674c8acb upstream. The block_len read from the host-supplied NTB header is checked against ntb_max but has no lower bound. When block_len is smaller than opts->ndp_size, the bounds check of: ndp_index > (block_len - opts->ndp_size) will underflow producing a huge unsigned value that ndp_index can never exceed, defeating the check entirely. The same underflow occurs in the datagram index checks against block_len - opts->dpe_size. With those checks neutered, a malicious USB host can choose ndp_index and datagram offsets that point past the actual transfer, and the skb_put_data() copies adjacent kernel memory into the network skb. Fix this by rejecting block lengths that cannot hold at least the NTB header plus one NDP. This will make block_len - opts->ndp_size and block_len - opts->dpe_size both well-defined. Commit 8d2b1a1ec9f5 ("CDC-NCM: avoid overflow in sanity checking") fixed a related class of issues on the host side of NCM. Fixes: 2b74b0a04d3e ("USB: gadget: f_ncm: add bounds checks to ncm_unwrap_ntb()") Cc: stable Assisted-by: gregkh_clanker_t1000 Link: https://patch.msgid.link/2026040753-baffle-handheld-624d@gregkh Signed-off-by: Greg Kroah-Hartman

usb: gadget: f_ncm: Fix MAC assignment NCM ethernet

2025-11-24T09:29:28+00:00

[ Upstream commit 956606bafb5fc6e5968aadcda86fc0037e1d7548 ] This fix is already present in f_ecm.c and was never propagated to f_ncm.c When creating multiple NCM ethernet devices on a composite usb gadget device each MAC address on the HOST side will be identical. Having the same MAC on different network interfaces is bad. This fix updates the MAC address inside the ncm_strings_defs global during the ncm_bind call. This ensures each device has a unique MAC. In f_ecm.c ecm_string_defs is updated in the same way. The defunct MAC assignment in ncm_alloc has been removed. Signed-off-by: raub camaioni Link: https://lore.kernel.org/r/20250815131358.1047525-1-raubcameo@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

usb: gadget: f_ncm: Refactor bind path to use __free()

2025-10-23T14:16:29+00:00

[ Upstream commit 75a5b8d4ddd4eb6b16cb0b475d14ff4ae64295ef ] After an bind/unbind cycle, the ncm->notify_req is left stale. If a subsequent bind fails, the unified error label attempts to free this stale request, leading to a NULL pointer dereference when accessing ep->ops->free_request. Refactor the error handling in the bind path to use the __free() automatic cleanup mechanism. Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020 Call trace: usb_ep_free_request+0x2c/0xec ncm_bind+0x39c/0x3dc usb_add_function+0xcc/0x1f0 configfs_composite_bind+0x468/0x588 gadget_bind_driver+0x104/0x270 really_probe+0x190/0x374 __driver_probe_device+0xa0/0x12c driver_probe_device+0x3c/0x218 __device_attach_driver+0x14c/0x188 bus_for_each_drv+0x10c/0x168 __device_attach+0xfc/0x198 device_initial_probe+0x14/0x24 bus_probe_device+0x94/0x11c device_add+0x268/0x48c usb_add_gadget+0x198/0x28c dwc3_gadget_init+0x700/0x858 __dwc3_set_mode+0x3cc/0x664 process_scheduled_works+0x1d8/0x488 worker_thread+0x244/0x334 kthread+0x114/0x1bc ret_from_fork+0x10/0x20 Fixes: 9f6ce4240a2b ("usb: gadget: f_ncm.c added") Cc: stable@kernel.org Signed-off-by: Kuen-Han Tsai Link: https://lore.kernel.org/r/20250916-ready-v1-3-4997bf277548@google.com Signed-off-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20250916-ready-v1-3-4997bf277548@google.com Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

usb: gadget: f_ncm: Fix UAF ncm object at re-bind after usb ep transport error

2024-04-27T15:11:40+00:00

commit 6334b8e4553cc69f51e383c9de545082213d785e upstream. When ncm function is working and then stop usb0 interface for link down, eth_stop() is called. At this piont, accidentally if usb transport error should happen in usb_ep_enable(), 'in_ep' and/or 'out_ep' may not be enabled. After that, ncm_disable() is called to disable for ncm unbind but gether_disconnect() is never called since 'in_ep' is not enabled. As the result, ncm object is released in ncm unbind but 'dev->port_usb' associated to 'ncm->port' is not NULL. And when ncm bind again to recover netdev, ncm object is reallocated but usb0 interface is already associated to previous released ncm object. Therefore, once usb0 interface is up and eth_start_xmit() is called, released ncm object is dereferrenced and it might cause use-after-free memory. [function unlink via configfs] usb0: eth_stop dev->port_usb=ffffff9b179c3200 --> error happens in usb_ep_enable(). NCM: ncm_disable: ncm=ffffff9b179c3200 --> no gether_disconnect() since ncm->port.in_ep->enabled is false. NCM: ncm_unbind: ncm unbind ncm=ffffff9b179c3200 NCM: ncm_free: ncm free ncm=ffffff9b179c3200 <-- released ncm [function link via configfs] NCM: ncm_alloc: ncm alloc ncm=ffffff9ac4f8a000 NCM: ncm_bind: ncm bind ncm=ffffff9ac4f8a000 NCM: ncm_set_alt: ncm=ffffff9ac4f8a000 alt=0 usb0: eth_open dev->port_usb=ffffff9b179c3200 <-- previous released ncm usb0: eth_start dev->port_usb=ffffff9b179c3200 <-- eth_start_xmit() --> dev->wrap() Unable to handle kernel paging request at virtual address dead00000000014f This patch addresses the issue by checking if 'ncm->netdev' is not NULL at ncm_disable() to call gether_disconnect() to deassociate 'dev->port_usb'. It's more reasonable to check 'ncm->netdev' to call gether_connect/disconnect rather than check 'ncm->port.in_ep->enabled' since it might not be enabled but the gether connection might be established. Signed-off-by: Norihiko Hama Cc: stable Link: https://lore.kernel.org/r/20240327023550.51214-1-Norihiko.Hama@alpsalpine.com Signed-off-by: Greg Kroah-Hartman

usb: gadget: ncm: Fix handling of zero block length packets

2024-04-03T13:28:42+00:00

commit f90ce1e04cbcc76639d6cba0fdbd820cd80b3c70 upstream. While connecting to a Linux host with CDC_NCM_NTB_DEF_SIZE_TX set to 65536, it has been observed that we receive short packets, which come at interval of 5-10 seconds sometimes and have block length zero but still contain 1-2 valid datagrams present. According to the NCM spec: "If wBlockLength = 0x0000, the block is terminated by a short packet. In this case, the USB transfer must still be shorter than dwNtbInMaxSize or dwNtbOutMaxSize. If exactly dwNtbInMaxSize or dwNtbOutMaxSize bytes are sent, and the size is a multiple of wMaxPacketSize for the given pipe, then no ZLP shall be sent. wBlockLength= 0x0000 must be used with extreme care, because of the possibility that the host and device may get out of sync, and because of test issues. wBlockLength = 0x0000 allows the sender to reduce latency by starting to send a very large NTB, and then shortening it when the sender discovers that there’s not sufficient data to justify sending a large NTB" However, there is a potential issue with the current implementation, as it checks for the occurrence of multiple NTBs in a single giveback by verifying if the leftover bytes to be processed is zero or not. If the block length reads zero, we would process the same NTB infintely because the leftover bytes is never zero and it leads to a crash. Fix this by bailing out if block length reads zero. Cc: stable@vger.kernel.org Fixes: 427694cfaafa ("usb: gadget: ncm: Handle decoding of multiple NTB's in unwrap call") Signed-off-by: Krishna Kurapati Reviewed-by: Maciej Żenczykowski Link: https://lore.kernel.org/r/20240228115441.2105585-1-quic_kriskura@quicinc.com Signed-off-by: Greg Kroah-Hartman

usb: gadget: ncm: Avoid dropping datagrams of properly parsed NTBs

2024-03-01T12:35:02+00:00

commit 76c51146820c5dac629f21deafab0a7039bc3ccd upstream. It is observed sometimes when tethering is used over NCM with Windows 11 as host, at some instances, the gadget_giveback has one byte appended at the end of a proper NTB. When the NTB is parsed, unwrap call looks for any leftover bytes in SKB provided by u_ether and if there are any pending bytes, it treats them as a separate NTB and parses it. But in case the second NTB (as per unwrap call) is faulty/corrupt, all the datagrams that were parsed properly in the first NTB and saved in rx_list are dropped. Adding a few custom traces showed the following: [002] d..1 7828.532866: dwc3_gadget_giveback: ep1out: req 000000003868811a length 1025/16384 zsI ==> 0 [002] d..1 7828.532867: ncm_unwrap_ntb: K: ncm_unwrap_ntb toprocess: 1025 [002] d..1 7828.532867: ncm_unwrap_ntb: K: ncm_unwrap_ntb nth: 1751999342 [002] d..1 7828.532868: ncm_unwrap_ntb: K: ncm_unwrap_ntb seq: 0xce67 [002] d..1 7828.532868: ncm_unwrap_ntb: K: ncm_unwrap_ntb blk_len: 0x400 [002] d..1 7828.532868: ncm_unwrap_ntb: K: ncm_unwrap_ntb ndp_len: 0x10 [002] d..1 7828.532869: ncm_unwrap_ntb: K: Parsed NTB with 1 frames In this case, the giveback is of 1025 bytes and block length is 1024. The rest 1 byte (which is 0x00) won't be parsed resulting in drop of all datagrams in rx_list. Same is case with packets of size 2048: [002] d..1 7828.557948: dwc3_gadget_giveback: ep1out: req 0000000011dfd96e length 2049/16384 zsI ==> 0 [002] d..1 7828.557949: ncm_unwrap_ntb: K: ncm_unwrap_ntb nth: 1751999342 [002] d..1 7828.557950: ncm_unwrap_ntb: K: ncm_unwrap_ntb blk_len: 0x800 Lecroy shows one byte coming in extra confirming that the byte is coming in from PC: Transfer 2959 - Bytes Transferred(1025) Timestamp((18.524 843 590) - Transaction 8391 - Data(1025 bytes) Timestamp(18.524 843 590) --- Packet 4063861 Data(1024 bytes) Duration(2.117us) Idle(14.700ns) Timestamp(18.524 843 590) --- Packet 4063863 Data(1 byte) Duration(66.160ns) Time(282.000ns) Timestamp(18.524 845 722) According to Windows driver, no ZLP is needed if wBlockLength is non-zero, because the non-zero wBlockLength has already told the function side the size of transfer to be expected. However, there are in-market NCM devices that rely on ZLP as long as the wBlockLength is multiple of wMaxPacketSize. To deal with such devices, it pads an extra 0 at end so the transfer is no longer multiple of wMaxPacketSize. Cc: Fixes: 9f6ce4240a2b ("usb: gadget: f_ncm.c added") Signed-off-by: Krishna Kurapati Reviewed-by: Maciej Żenczykowski Link: https://lore.kernel.org/r/20240205074650.200304-1-quic_kriskura@quicinc.com Signed-off-by: Greg Kroah-Hartman

usb: gadget: f_ncm: Always set current gadget in ncm_bind()

2023-11-28T17:19:45+00:00

[ Upstream commit a04224da1f3424b2c607b12a3bd1f0e302fb8231 ] Previously, gadget assignment to the net device occurred exclusively during the initial binding attempt. Nevertheless, the gadget pointer could change during bind/unbind cycles due to various conditions, including the unloading/loading of the UDC device driver or the detachment/reconnection of an OTG-capable USB hub device. This patch relocates the gether_set_gadget() function out from ncm_opts->bound condition check, ensuring that the correct gadget is assigned during each bind request. The provided logs demonstrate the consistency of ncm_opts throughout the power cycle, while the gadget may change. * OTG hub connected during boot up and assignment of gadget and ncm_opts pointer [ 2.366301] usb 2-1.5: New USB device found, idVendor=2996, idProduct=0105 [ 2.366304] usb 2-1.5: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [ 2.366306] usb 2-1.5: Product: H2H Bridge [ 2.366308] usb 2-1.5: Manufacturer: Aptiv [ 2.366309] usb 2-1.5: SerialNumber: 13FEB2021 [ 2.427989] usb 2-1.5: New USB device found, VID=2996, PID=0105 [ 2.428959] dabridge 2-1.5:1.0: dabridge 2-4 total endpoints=5, 0000000093a8d681 [ 2.429710] dabridge 2-1.5:1.0: P(0105) D(22.06.22) F(17.3.16) H(1.1) high-speed [ 2.429714] dabridge 2-1.5:1.0: Hub 2-2 P(0151) V(06.87) [ 2.429956] dabridge 2-1.5:1.0: All downstream ports in host mode [ 2.430093] gadget 000000003c414d59 ------> gadget pointer * NCM opts and associated gadget pointer during First ncm_bind [ 34.763929] NCM opts 00000000aa304ac9 [ 34.763930] NCM gadget 000000003c414d59 * OTG capable hub disconnecte or assume driver unload. [ 97.203114] usb 2-1: USB disconnect, device number 2 [ 97.203118] usb 2-1.1: USB disconnect, device number 3 [ 97.209217] usb 2-1.5: USB disconnect, device number 4 [ 97.230990] dabr_udc deleted * Reconnect the OTG hub or load driver assaign new gadget pointer. [ 111.534035] usb 2-1.1: New USB device found, idVendor=2996, idProduct=0120, bcdDevice= 6.87 [ 111.534038] usb 2-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [ 111.534040] usb 2-1.1: Product: Vendor [ 111.534041] usb 2-1.1: Manufacturer: Aptiv [ 111.534042] usb 2-1.1: SerialNumber: Superior [ 111.535175] usb 2-1.1: New USB device found, VID=2996, PID=0120 [ 111.610995] usb 2-1.5: new high-speed USB device number 8 using xhci-hcd [ 111.630052] usb 2-1.5: New USB device found, idVendor=2996, idProduct=0105, bcdDevice=21.02 [ 111.630055] usb 2-1.5: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [ 111.630057] usb 2-1.5: Product: H2H Bridge [ 111.630058] usb 2-1.5: Manufacturer: Aptiv [ 111.630059] usb 2-1.5: SerialNumber: 13FEB2021 [ 111.687464] usb 2-1.5: New USB device found, VID=2996, PID=0105 [ 111.690375] dabridge 2-1.5:1.0: dabridge 2-8 total endpoints=5, 000000000d87c961 [ 111.691172] dabridge 2-1.5:1.0: P(0105) D(22.06.22) F(17.3.16) H(1.1) high-speed [ 111.691176] dabridge 2-1.5:1.0: Hub 2-6 P(0151) V(06.87) [ 111.691646] dabridge 2-1.5:1.0: All downstream ports in host mode [ 111.692298] gadget 00000000dc72f7a9 --------> new gadget ptr on connect * NCM opts and associated gadget pointer during second ncm_bind [ 113.271786] NCM opts 00000000aa304ac9 -----> same opts ptr used during first bind [ 113.271788] NCM gadget 00000000dc72f7a9 ----> however new gaget ptr, that will not set in net_device due to ncm_opts->bound = true Signed-off-by: Hardik Gajjar Link: https://lore.kernel.org/r/20231020153324.82794-1-hgajjar@de.adit-jv.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

usb: gadget: ncm: Handle decoding of multiple NTB's in unwrap call

2023-10-02T11:38:10+00:00

When NCM is used with hosts like Windows PC, it is observed that there are multiple NTB's contained in one usb request giveback. Since the driver unwraps the obtained request data assuming only one NTB is present, we loose the subsequent NTB's present resulting in data loss. Fix this by checking the parsed block length with the obtained data length in usb request and continue parsing after the last byte of current NTB. Cc: stable@vger.kernel.org Fixes: 9f6ce4240a2b ("usb: gadget: f_ncm.c added") Signed-off-by: Krishna Kurapati Reviewed-by: Maciej Żenczykowski Link: https://lore.kernel.org/r/20230927105858.12950-1-quic_kriskura@quicinc.com Signed-off-by: Greg Kroah-Hartman