In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: printer: fix infinite loop in printer_read()
printer_read() uses the same variable for the requested copy size and the number of bytes actually copied to user space. copy_to_user() returns the number of bytes not copied, so when it fails to copy anything, the computed copied length becomes zero.
In that case len, buf, current_rx_bytes and current_rx_buf are left unchanged. If RX data is available and the user buffer remains unwritable, the read loop can repeat indefinitely.
Track the copied length separately and return -EFAULT, or the number of bytes already copied, if an iteration makes no progress.
References
- https://git.kernel.org/stable/c/4cde0b38cc0cb8b7dc17295801015148de37d1d2
- https://git.kernel.org/stable/c/994afccfdcceb73be33f69a8a8ea71e260c9eca5
- https://git.kernel.org/stable/c/c2e819be6a5c7f34344926b4bd7e3dfca58cf48a
- https://git.kernel.org/stable/c/e03597ad9494b500344076589aeaa6c6d2d381d3
- https://git.kernel.org/stable/c/e41bbbbb1740ce4d7270ab1cdeca13892d6a8d2e