On Wed, Mar 17, 2021 at 8:43 AM Gustavo A. R. Silva
<gustavo...@kernel.org> wrote:
> Fix the following out-of-bounds warning by replacing the one-element
> array in an anonymous union with a pointer:
>
> CC [M] drivers/net/ethernet/intel/ixgbe/ixgbe_common.o
> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c: In function
> ‘ixgbe_host_interface_command’:
> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3729:13: warning: array
> subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’}
> [-Warray-bounds]
> 3729 | bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
> | ~~~~~~~~~~^~~~
> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3682:7: note: while
> referencing ‘u32arr’
> 3682 | u32 u32arr[1];
> | ^~~~~~
>
> This helps with the ongoing efforts to globally enable -Warray-bounds.
>
> Notice that, the usual approach to fix these sorts of issues is to
> replace the one-element array with a flexible-array member. However,
> flexible arrays should not be used in unions. That, together with the
> fact that the array notation is not being affected in any ways, is why
> the pointer approach was chosen in this case.
>
> Link: https://github.com/KSPP/linux/issues/109
> Signed-off-by: Gustavo A. R. Silva <gustavo...@kernel.org>
> ---
> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> index 62ddb452f862..bff3dc1af702 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> @@ -3679,7 +3679,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw,
> void *buffer,
> u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
> union {
> struct ixgbe_hic_hdr hdr;
> - u32 u32arr[1];
> + u32 *u32arr;
> } *bp = buffer;
> u16 buf_len, dword_len;
> s32 status;
This looks bogus. An array is inline, a pointer points elsewhere -
they're not interchangeable.
