iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

net: ena: Fix potential sign extension issue

Browse Source 
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>
This commit is contained in:
David Arinzon 2024-04-10 09:13:55 +00:00 committed by Paolo Abeni
parent fe3eb40672
commit 713a85195a
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/net/ethernet/amazon/ena/ena_com.c
View File

@ -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);