5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Arinzon darinzon@amazon.com
[ 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: 689b2bdaaa14 ("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 --- drivers/net/ethernet/amazon/ena/ena_com.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c b/drivers/net/ethernet/amazon/ena/ena_com.c index 29700fee42e9d..46a796576f6b6 100644 --- a/drivers/net/ethernet/amazon/ena/ena_com.c +++ b/drivers/net/ethernet/amazon/ena/ena_com.c @@ -374,7 +374,7 @@ static int ena_com_init_io_sq(struct ena_com_dev *ena_dev, ENA_COM_BOUNCE_BUFFER_CNTRL_CNT; io_sq->bounce_buf_ctrl.next_to_use = 0;
- size = io_sq->bounce_buf_ctrl.buffer_size * + size = (size_t)io_sq->bounce_buf_ctrl.buffer_size * io_sq->bounce_buf_ctrl.buffers_num;
dev_node = dev_to_node(ena_dev->dmadev);