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The kernel has only two users of proc_do_large_bitmap(), the kernel CPU watchdog, and the ip_local_reserved_ports. Refer to watchdog_cpumask and ip_local_reserved_ports in Documentation for further details on these. When you input a large buffer into these, when it is larger than PAGE_SIZE- 1, the input data gets misparsed, and the user get incorrectly informed that the desired input value was set. This commit implements a test which mimics and exploits that use case, it uses a bitmap size, as in the watchdog case. The bitmap is used to test the bitmap proc handler, proc_do_large_bitmap(). The next commit fixes this issue. [akpm@linux-foundation.org: move proc_do_large_bitmap() export to EOF] [mcgrof@kernel.org: use new target description for backward compatibility] [mcgrof@kernel.org: augment test number to 50, ran into issues with bash string comparisons when testing up to 50 cases.] [mcgrof@kernel.org: introduce and use verify_diff_proc_file() to use diff] [mcgrof@kernel.org: use mktemp for tmp file] [mcgrof@kernel.org: merge shell test and C code] [mcgrof@kernel.org: commit log love] [mcgrof@kernel.org: export proc_do_large_bitmap() to allow for the test [mcgrof@kernel.org: check for the return value when writing to the proc file] Link: http://lkml.kernel.org/r/20190320222831.8243-6-mcgrof@kernel.org Signed-off-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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.