Michal Pecio fe1ccba52a usb: xhci: Skip only one TD on Ring Underrun/Overrun
If skipping is deferred to events other than Missed Service Error itsef,
it means we are running on an xHCI 1.0 host and don't know how many TDs
were missed until we reach some ordinary transfer completion event.

And in case of ring xrun, we can't know where the xrun happened either.

If we skip all pending TDs, we may prematurely give back TDs added after
the xrun had occurred, risking data loss or buffer UAF by the xHC.

If we skip none, a driver may become confused and stop working when all
its URBs are missed and appear to be "in flight" forever.

Skip exactly one TD on each xrun event - the first one that was missed,
as we can now be sure that the HC has finished processing it. Provided
that one more TD is queued before any subsequent doorbell ring, it will
become safe to skip another TD by the time we get an xrun again.

Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250306144954.3507700-8-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-03-06 16:46:16 +01:00
2025-02-16 14:02:44 -08:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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