From: "Nelson, Shannon" <shannon.nelson@amd.com>
To: darinzon@amazon.com, David Miller <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org
Cc: "Woodhouse, David" <dwmw@amazon.com>,
"Machulsky, Zorik" <zorik@amazon.com>,
"Matushevsky, Alexander" <matua@amazon.com>,
Saeed Bshara <saeedb@amazon.com>, "Wilson, Matt" <msw@amazon.com>,
"Liguori, Anthony" <aliguori@amazon.com>,
"Bshara, Nafea" <nafea@amazon.com>,
"Belgazal, Netanel" <netanel@amazon.com>,
"Saidi, Ali" <alisaidi@amazon.com>,
"Herrenschmidt, Benjamin" <benh@amazon.com>,
"Kiyanovski, Arthur" <akiyano@amazon.com>,
"Dagan, Noam" <ndagan@amazon.com>,
"Agroskin, Shay" <shayagr@amazon.com>,
"Itzko, Shahar" <itzko@amazon.com>,
"Abboud, Osama" <osamaabb@amazon.com>,
"Ostrovsky, Evgeny" <evostrov@amazon.com>,
"Tabachnik, Ofir" <ofirt@amazon.com>,
Netanel Belgazal <netanel@annapurnalabs.com>,
Sameeh Jubran <sameehj@amazon.com>
Subject: Re: [PATCH v1 net 1/4] net: ena: Fix potential sign extension issue
Date: Wed, 10 Apr 2024 14:49:02 -0700 [thread overview]
Message-ID: <eb4f8216-a25d-4622-a9df-de3c7b4558dd@amd.com> (raw)
In-Reply-To: <20240410091358.16289-2-darinzon@amazon.com>
On 4/10/2024 2:13 AM, darinzon@amazon.com wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
>
>
> From: David Arinzon <darinzon@amazon.com>
>
> 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>
> ---
> 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 9e9e4a03..2d8a66ea 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);
> --
> 2.40.1
>
>
next prev parent reply other threads:[~2024-04-10 21:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-10 9:13 [PATCH v1 net 0/4] ENA driver bug fixes darinzon
2024-04-10 9:13 ` [PATCH v1 net 1/4] net: ena: Fix potential sign extension issue darinzon
2024-04-10 21:49 ` Nelson, Shannon [this message]
2024-04-10 9:13 ` [PATCH v1 net 2/4] net: ena: Wrong missing IO completions check order darinzon
2024-04-10 21:51 ` Nelson, Shannon
2024-04-10 9:13 ` [PATCH v1 net 3/4] net: ena: Fix incorrect descriptor free behavior darinzon
2024-04-10 21:52 ` Nelson, Shannon
2024-04-10 9:13 ` [PATCH v1 net 4/4] net: ena: Set tx_info->xdpf value to NULL darinzon
2024-04-10 21:53 ` Nelson, Shannon
2024-04-11 9:40 ` [PATCH v1 net 0/4] ENA driver bug fixes patchwork-bot+netdevbpf
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