ixgbe: Fix out-bounds warning in ixgbe_host_interface_command()

Replace union with a couple of pointers in order to fix the following
out-of-bounds warning:

  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.

Link: https://github.com/KSPP/linux/issues/109
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20210527173424.362456-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
index 03ccbe6..e90b504 100644 (file)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
@@ -3678,10 +3678,8 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, void *buffer,
                                 bool return_data)
 {
        u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
-       union {
-               struct ixgbe_hic_hdr hdr;
-               u32 u32arr[1];
-       } *bp = buffer;
+       struct ixgbe_hic_hdr *hdr = buffer;
+       u32 *u32arr = buffer;
        u16 buf_len, dword_len;
        s32 status;
        u32 bi;
@@ -3707,12 +3705,12 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, void *buffer,
 
        /* first pull in the header so we know the buffer length */
        for (bi = 0; bi < dword_len; bi++) {
-               bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
-               le32_to_cpus(&bp->u32arr[bi]);
+               u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
+               le32_to_cpus(&u32arr[bi]);
        }
 
        /* If there is any thing in data position pull it in */
-       buf_len = bp->hdr.buf_len;
+       buf_len = hdr->buf_len;
        if (!buf_len)
                goto rel_out;
 
@@ -3727,8 +3725,8 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, void *buffer,
 
        /* Pull in the rest of the buffer (bi is where we left off) */
        for (; bi <= dword_len; bi++) {
-               bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
-               le32_to_cpus(&bp->u32arr[bi]);
+               u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
+               le32_to_cpus(&u32arr[bi]);
        }
 
 rel_out: