net: ena: Fix potential sign extension issue

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[ Upstream commit 713a85195a ]

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>

...

This commit is contained in:

David Arinzon 2024-04-10 09:13:55 +00:00 • committed by Greg Kroah-Hartman

parent 507cc232ff

commit 4d142dda05

1 changed files with 1 additions and 1 deletions

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drivers/net/ethernet/amazon/ena/ena_com.c

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