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168b84d5d2
The MIPS implementation of access_ok() incorrectly reports that access
to the final byte of user memory is not OK, much as the alpha & SH
versions did prior to commit 94bd8a05cd ("Fix 'acccess_ok()' on alpha
and SH").
For example on a MIPS64 system with __UA_LIMIT == 0xffff000000000000 we
incorrectly fail in the following cases:
access_ok(0xffffffffffff, 0x1) = 0
access_ok(0xfffffffffffe, 0x2) = 0
Fix MIPS in the same way as alpha & SH, by subtracting one from the addr
+ size condition when size is non-zero. With this the access_ok() calls
above return 1 indicating that the access may be valid.
The cost of the improved check is pretty minimal - we gain 2410 bytes,
or 0.03%, in kernel code size for a 64r6el_defconfig kernel built using
GCC 8.1.0.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
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.