kernel.git/drivers/usb/gadget/function/u_serial.c, branch linux-5.4.y

usb: gadget: u_serial: Fix race condition in TTY wakeup

2025-07-17T16:25:03Z

commit c529c3730bd09115684644e26bf01ecbd7e2c2c9 upstream. A race condition occurs when gs_start_io() calls either gs_start_rx() or gs_start_tx(), as those functions briefly drop the port_lock for usb_ep_queue(). This allows gs_close() and gserial_disconnect() to clear port.tty and port_usb, respectively. Use the null-safe TTY Port helper function to wake up TTY. Example CPU1: CPU2: gserial_connect() // lock gs_close() // await lock gs_start_rx() // unlock usb_ep_queue() gs_close() // lock, reset port.tty and unlock gs_start_rx() // lock tty_wakeup() // NPE Fixes: 35f95fd7f234 ("TTY: usb/u_serial, use tty from tty_port") Cc: stable Signed-off-by: Kuen-Han Tsai Reviewed-by: Prashanth K Link: https://lore.kernel.org/linux-usb/20240116141801.396398-1-khtsai@google.com/ Link: https://lore.kernel.org/r/20250617050844.1848232-2-khtsai@google.com Signed-off-by: Greg Kroah-Hartman

Revert "usb: gadget: u_serial: Disable ep before setting port to null to fix the crash caused by port being null"

2025-02-01T17:18:53Z

commit 086fd062bc3883ae1ce4166cff5355db315ad879 upstream. This reverts commit 13014969cbf07f18d62ceea40bd8ca8ec9d36cec. It is reported to cause crashes on Tegra systems, so revert it for now. Link: https://lore.kernel.org/r/1037c1ad-9230-4181-b9c3-167dbaa47644@nvidia.com Reported-by: Jon Hunter Cc: stable Cc: Lianqin Hu Link: https://lore.kernel.org/r/2025011711-yippee-fever-a737@gregkh Signed-off-by: Greg Kroah-Hartman

usb: gadget: u_serial: Disable ep before setting port to null to fix the crash caused by port being null

2025-02-01T17:18:47Z

commit 13014969cbf07f18d62ceea40bd8ca8ec9d36cec upstream. Considering that in some extreme cases, when performing the unbinding operation, gserial_disconnect has cleared gser->ioport, which triggers gadget reconfiguration, and then calls gs_read_complete, resulting in access to a null pointer. Therefore, ep is disabled before gserial_disconnect sets port to null to prevent this from happening. Call trace: gs_read_complete+0x58/0x240 usb_gadget_giveback_request+0x40/0x160 dwc3_remove_requests+0x170/0x484 dwc3_ep0_out_start+0xb0/0x1d4 __dwc3_gadget_start+0x25c/0x720 kretprobe_trampoline.cfi_jt+0x0/0x8 kretprobe_trampoline.cfi_jt+0x0/0x8 udc_bind_to_driver+0x1d8/0x300 usb_gadget_probe_driver+0xa8/0x1dc gadget_dev_desc_UDC_store+0x13c/0x188 configfs_write_iter+0x160/0x1f4 vfs_write+0x2d0/0x40c ksys_write+0x7c/0xf0 __arm64_sys_write+0x20/0x30 invoke_syscall+0x60/0x150 el0_svc_common+0x8c/0xf8 do_el0_svc+0x28/0xa0 el0_svc+0x24/0x84 Fixes: c1dca562be8a ("usb gadget: split out serial core") Cc: stable Suggested-by: Greg Kroah-Hartman Signed-off-by: Lianqin Hu Link: https://lore.kernel.org/r/TYUPR06MB621733B5AC690DBDF80A0DCCD2042@TYUPR06MB6217.apcprd06.prod.outlook.com Signed-off-by: Greg Kroah-Hartman

usb: gadget: u_serial: Fix the issue that gs_start_io crashed due to accessing null pointer

2024-12-19T17:05:02Z

commit 4cfbca86f6a8b801f3254e0e3c8f2b1d2d64be2b upstream. Considering that in some extreme cases, when u_serial driver is accessed by multiple threads, Thread A is executing the open operation and calling the gs_open, Thread B is executing the disconnect operation and calling the gserial_disconnect function,The port->port_usb pointer will be set to NULL. E.g. Thread A Thread B gs_open() gadget_unbind_driver() gs_start_io() composite_disconnect() gs_start_rx() gserial_disconnect() ... ... spin_unlock(&port->port_lock) status = usb_ep_queue() spin_lock(&port->port_lock) spin_lock(&port->port_lock) port->port_usb = NULL gs_free_requests(port->port_usb->in) spin_unlock(&port->port_lock) Crash This causes thread A to access a null pointer (port->port_usb is null) when calling the gs_free_requests function, causing a crash. If port_usb is NULL, the release request will be skipped as it will be done by gserial_disconnect. So add a null pointer check to gs_start_io before attempting to access the value of the pointer port->port_usb. Call trace: gs_start_io+0x164/0x25c gs_open+0x108/0x13c tty_open+0x314/0x638 chrdev_open+0x1b8/0x258 do_dentry_open+0x2c4/0x700 vfs_open+0x2c/0x3c path_openat+0xa64/0xc60 do_filp_open+0xb8/0x164 do_sys_openat2+0x84/0xf0 __arm64_sys_openat+0x70/0x9c invoke_syscall+0x58/0x114 el0_svc_common+0x80/0xe0 do_el0_svc+0x1c/0x28 el0_svc+0x38/0x68 Fixes: c1dca562be8a ("usb gadget: split out serial core") Cc: stable@vger.kernel.org Suggested-by: Prashanth K Signed-off-by: Lianqin Hu Acked-by: Prashanth K Link: https://lore.kernel.org/r/TYUPR06MB62178DC3473F9E1A537DCD02D2362@TYUPR06MB6217.apcprd06.prod.outlook.com Signed-off-by: Greg Kroah-Hartman

usb: gadget: serial: fix Tx stall after buffer overflow

2020-03-12T12:00:10Z

[ Upstream commit e4bfded56cf39b8d02733c1e6ef546b97961e18a ] Symptom: application opens /dev/ttyGS0 and starts sending (writing) to it while either USB cable is not connected, or nobody listens on the other side of the cable. If driver circular buffer overflows before connection is established, no data will be written to the USB layer until/unless /dev/ttyGS0 is closed and re-opened again by the application (the latter besides having no means of being notified about the event of establishing of the connection.) Fix: on open and/or connect, kick Tx to flush circular buffer data to USB layer. Signed-off-by: Sergey Organov Reviewed-by: Michał Mirosław Signed-off-by: Felipe Balbi Signed-off-by: Sasha Levin

usb: gadget: u_serial: add missing port entry locking

2019-12-13T07:42:20Z

commit daf82bd24e308c5a83758047aff1bd81edda4f11 upstream. gserial_alloc_line() misses locking (for a release barrier) while resetting port entry on TTY allocation failure. Fix this. Cc: stable@vger.kernel.org Signed-off-by: Michał Mirosław Reviewed-by: Greg Kroah-Hartman Tested-by: Ladislav Michl Signed-off-by: Felipe Balbi Signed-off-by: Greg Kroah-Hartman

usb: gadget: u_serial: process RX in workqueue instead of tasklet

2019-01-28T10:51:30Z

Switch RX processing from tasklet to (delayed) work queue. This allows receiver more room to process incoming data and prevents flood of "ttyGS0: RX not scheduled?" messages on HS receive on slow CPU. A side effect is 2.4MB/s zmodem transfer speed (up from 1.8MB/s) on my test board. Signed-off-by: Michał Mirosław Signed-off-by: Felipe Balbi

usb: gadget: u_serial: Use kfifo instead of homemade circular buffer

2017-12-11T10:36:50Z

The kernel FIFO implementation, kfifo, provides interfaces to manipulate a first-in-first-out circular buffer. Use kfifo instead of the homemade one to make the code more concise and readable. Signed-off-by: Lu Baolu Signed-off-by: Felipe Balbi

USB: gadget: function: Remove redundant license text

2017-11-07T14:45:02Z

Now that the SPDX tag is in all USB files, that identifies the license in a specific and legally-defined manner. So the extra GPL text wording can be removed as it is no longer needed at all. This is done on a quest to remove the 700+ different ways that files in the kernel describe the GPL license text. And there's unneeded stuff like the address (sometimes incorrect) for the FSF which is never needed. No copyright headers or other non-license-description text was removed. Cc: Oliver Neukum Cc: Johan Hovold Cc: Jerry Zhang Cc: John Keeping Cc: Krzysztof Opasiak Cc: Abdulhadi Mohamed Cc: Matthew Wilcox Cc: Janusz Dziedzic Acked-by: Felipe Balbi Acked-by: Michal Nazarewicz Acked-by: Laurent Pinchart Acked-by: Vincent Pelletier Signed-off-by: Greg Kroah-Hartman

USB: add SPDX identifiers to all remaining files in drivers/usb/

2017-11-04T10:48:02Z

It's good to have SPDX identifiers in all files to make it easier to audit the kernel tree for correct licenses. Update the drivers/usb/ and include/linux/usb* files with the correct SPDX license identifier based on the license text in the file itself. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This work is based on a script and data from Thomas Gleixner, Philippe Ombredanne, and Kate Stewart. Cc: Thomas Gleixner Cc: Kate Stewart Cc: Philippe Ombredanne Signed-off-by: Greg Kroah-Hartman Acked-by: Felipe Balbi Acked-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman