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Jann Horn b9472f7d82 firmware: xilinx: fix debugfs write handler
- Userspace wants to write a string with `len` bytes, not counting the
   terminating NULL, so we should allocate `len+1` bytes. It looks like the
   current code relied on having a nullbyte directly behind `kern_buff`,
   which happens to work reliably as long as `len` isn't one of the kmalloc
   size classes.
 - strncpy_from_user() is completely wrong here; userspace is giving us a
   (not necessarily null-terminated) buffer and its length.
   strncpy_from_user() is for cases in which we don't know the length.
 - Don't let broken userspace allocate arbitrarily big kmalloc allocations.

Just use memdup_user_nul(), which is designed precisely for things like
this.

Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Jolly Shah <jolly.shah@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
2019-03-18 13:43:54 +01:00
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README

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 Restructured Text 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.