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[ Upstream commit c0e824661f443b8cab3897006c1bbc69fd0e7bc4 ]
memset() description in ISO/IEC 9899:1999 (and elsewhere) says:
The memset function copies the value of c (converted to an
unsigned char) into each of the first n characters of the
object pointed to by s.
The kernel's arm32 memset does not cast c to unsigned char. This results
in the following code to produce erroneous output:
char a[128];
memset(a, -128, sizeof(a));
This is because gcc will generally emit the following code before
it calls memset() :
mov r0, r7
mvn r1, #127 ; 0x7f
bl 00000000 <memset>
r1 ends up with 0xffffff80 before being used by memset() and the
'a' array will have -128 once in every four bytes while the other
bytes will be set incorrectly to -1 like this (printing the first
8 bytes) :
test_module: -128 -1 -1 -1
test_module: -1 -1 -1 -128
The change here is to 'and' r1 with 255 before it is used.
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Kursad Oney <kursad.oney@broadcom.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.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.