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commit2b405533c2upstream. commit2b74b0a04d("USB: gadget: f_ncm: add bounds checks to ncm_unwrap_ntb()") adds important bounds checking however it unfortunately also introduces a bug with respect to section 3.3.1 of the NCM specification. wDatagramIndex[1] : "Byte index, in little endian, of the second datagram described by this NDP16. If zero, then this marks the end of the sequence of datagrams in this NDP16." wDatagramLength[1]: "Byte length, in little endian, of the second datagram described by this NDP16. If zero, then this marks the end of the sequence of datagrams in this NDP16." wDatagramIndex[1] and wDatagramLength[1] respectively then may be zero but that does not mean we should throw away the data referenced by wDatagramIndex[0] and wDatagramLength[0] as is currently the case. Breaking the loop on (index2 == 0 || dg_len2 == 0) should come at the end as was previously the case and checks for index2 and dg_len2 should be removed since zero is valid. I'm not sure how much testing the above patch received but for me right now after enumeration ping doesn't work. Reverting the commit restores ping, scp, etc. The extra validation associated with wDatagramIndex[0] and wDatagramLength[0] appears to be valid so, this change removes the incorrect restriction on wDatagramIndex[1] and wDatagramLength[1] restoring data processing between host and device. Fixes:2b74b0a04d("USB: gadget: f_ncm: add bounds checks to ncm_unwrap_ntb()") Cc: Ilja Van Sprundel <ivansprundel@ioactive.com> Cc: Brooke Basile <brookebasile@gmail.com> Cc: stable <stable@kernel.org> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org> Link: https://lore.kernel.org/r/20200920170158.1217068-1-bryan.odonoghue@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.