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845d584f41
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
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| atm | ||
| c67x00 | ||
| chipidea | ||
| class | ||
| common | ||
| core | ||
| dwc2 | ||
| dwc3 | ||
| early | ||
| gadget | ||
| host | ||
| image | ||
| isp1760 | ||
| misc | ||
| mon | ||
| mtu3 | ||
| musb | ||
| phy | ||
| renesas_usbhs | ||
| serial | ||
| storage | ||
| typec | ||
| usbip | ||
| wusbcore | ||
| Kconfig | ||
| Makefile | ||
| README | ||
| usb-skeleton.c | ||
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.