1. 27 Oct, 2017 1 commit
    • Hans de Goede's avatar
      USB: devio: Revert "USB: devio: Don't corrupt user memory" · ee0ea51a
      Hans de Goede authored
      commit 845d584f upstream.
      
      Taking the uurb->buffer_length userspace passes in as a maximum for the
      actual urbs transfer_buffer_length causes 2 serious issues:
      
      1) It breaks isochronous support for all userspace apps using libusb,
         as existing libusb versions pass in 0 for uurb->buffer_length,
         relying on the kernel using the lenghts of the usbdevfs_iso_packet_desc
         descriptors passed in added together as buffer length.
      
         This for example causes redirection of USB audio and Webcam's into
         virtual machines using qemu-kvm to no longer work. This is a userspace
         ABI break and as such must be reverted.
      
         Note that the original commit does not protect other users / the
         kernels memory, it only stops the userspace process making the call
         from shooting itself in the foot.
      
      2) It may cause the kernel to program host controllers to DMA over random
         memory. Just as the devio code used to only look at the iso_packet_desc
         lenghts, the host drivers do the same, relying on the submitter of the
         urbs to make sure the entire buffer is large enough and not checking
         transfer_buffer_length.
      
         But the "USB: devio: Don't corrupt user memory" commit now takes the
         userspace provided uurb->buffer_length for the buffer-size while copying
         over the user-provided iso_packet_desc lengths 1:1, allowing the user
         to specify a small buffer size while programming the host controller to
         dma a lot more data.
      
         (Atleast the ohci, uhci, xhci and fhci drivers do not check
          transfer_buffer_length for isoc transfers.)
      
      This reverts commit fa1ed74e ("USB: devio: Don't corrupt user memory")
      fixing both these issues.
      
      Cc: Dan Carpenter <dan.carpenter@oracle.com>
      Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
      Acked-by: default avatarAlan Stern <stern@rowland.harvard.edu>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      ee0ea51a
  2. 21 Oct, 2017 39 commits