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4dea83d483
[ Upstream commit 713a85195aad25d8a26786a37b674e3e5ec09e3c ]
Small unsigned types are promoted to larger signed types in
the case of multiplication, the result of which may overflow.
In case the result of such a multiplication has its MSB
turned on, it will be sign extended with '1's.
This changes the multiplication result.
Code example of the phenomenon:
-------------------------------
u16 x, y;
size_t z1, z2;
x = y = 0xffff;
printk("x=%x y=%x\n",x,y);
z1 = x*y;
z2 = (size_t)x*y;
printk("z1=%lx z2=%lx\n", z1, z2);
Output:
-------
x=ffff y=ffff
z1=fffffffffffe0001 z2=fffe0001
The expected result of ffff*ffff is fffe0001, and without the
explicit casting to avoid the unwanted sign extension we got
fffffffffffe0001.
This commit adds an explicit casting to avoid the sign extension
issue.
Fixes: 689b2bdaaa ("net: ena: add functions for handling Low Latency Queues in ena_com")
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David Arinzon <darinzon@amazon.com>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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.