From: HyeongJun An <sammiee5311@gmail.com> stable inclusion from stable-v6.6.143 commit a1288cd700f721c1a119c4f1e8efa234e59caada category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/15880 CVE: CVE-2026-53194 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 96d47e40bf9db4a9efd5c8fb53287a508d165f14 upstream. klsi_105_prepare_write_buffer() is called by the generic write path with the bulk-out buffer and its size (bulk_out_size, 64 bytes). It stores a two-byte length header at the start of the buffer and copies the payload from the write fifo starting at buf + KLSI_HDR_LEN, but passes the full buffer size as the number of bytes to copy: count = kfifo_out_locked(&port->write_fifo, buf + KLSI_HDR_LEN, size, &port->lock); When the fifo holds at least size bytes, size bytes are copied starting two bytes into the size-byte buffer, writing KLSI_HDR_LEN bytes past its end. Copy at most size - KLSI_HDR_LEN bytes instead, leaving room for the header as safe_serial already does. Writing bulk_out_size or more bytes to the tty triggers a slab out-of-bounds write, observed with KASAN by emulating the device with dummy_hcd and raw-gadget: BUG: KASAN: slab-out-of-bounds in kfifo_copy_out+0x83/0xc0 Write of size 64 at addr ffff888112c62202 by task python3 kfifo_copy_out klsi_105_prepare_write_buffer [kl5kusb105] usb_serial_generic_write_start [usbserial] Allocated by task 139: usb_serial_probe [usbserial] The buggy address is located 2 bytes inside of allocated 64-byte region The out-of-bounds write no longer occurs with this change applied. Fixes: 60b3013cdaf3 ("USB: kl5usb105: reimplement using generic framework") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: HyeongJun An <sammiee5311@gmail.com> Signed-off-by: Johan Hovold <johan@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> --- drivers/usb/serial/kl5kusb105.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/usb/serial/kl5kusb105.c b/drivers/usb/serial/kl5kusb105.c index 5ee48b0650c4..472043568d6a 100644 --- a/drivers/usb/serial/kl5kusb105.c +++ b/drivers/usb/serial/kl5kusb105.c @@ -361,8 +361,8 @@ static int klsi_105_prepare_write_buffer(struct usb_serial_port *port, unsigned char *buf = dest; int count; - count = kfifo_out_locked(&port->write_fifo, buf + KLSI_HDR_LEN, size, - &port->lock); + count = kfifo_out_locked(&port->write_fifo, buf + KLSI_HDR_LEN, + size - KLSI_HDR_LEN, &port->lock); put_unaligned_le16(count, buf); return count + KLSI_HDR_LEN; -- 2.34.1