From 713a85195aad25d8a26786a37b674e3e5ec09e3c Mon Sep 17 00:00:00 2001 From: David Arinzon Date: Wed, 10 Apr 2024 09:13:55 +0000 Subject: net: ena: Fix potential sign extension issue 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 Signed-off-by: David Arinzon Reviewed-by: Shannon Nelson Signed-off-by: Paolo Abeni --- 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 9e9e4a03f1a8c..2d8a66ea82fab 100644 --- a/drivers/net/ethernet/amazon/ena/ena_com.c +++ b/drivers/net/ethernet/amazon/ena/ena_com.c @@ -351,7 +351,7 @@ 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); -- cgit 1.2.3-korg