On Thu, Sep 15, 2022 at 02:30:58PM +0300, Dan Carpenter wrote:
> A couple years back we went through the kernel an automatically
> converted size calculations to use struct_size() instead. The
> struct_size() calculation is protected against integer overflows.
>
> However it does not make sense to use the result from struct_size()
> for additional math operations as that would negate any safeness.
>
> Fixes: 1f3b69b6b939 ("i2c: mux: Use struct_size() in devm_kzalloc()")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> drivers/i2c/i2c-mux.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
> index 774507b54b57..313904be5f3b 100644
> --- a/drivers/i2c/i2c-mux.c
> +++ b/drivers/i2c/i2c-mux.c
> @@ -243,9 +243,10 @@ struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
> int (*deselect)(struct i2c_mux_core *, u32))
> {
> struct i2c_mux_core *muxc;
> + size_t mux_size;
>
> - muxc = devm_kzalloc(dev, struct_size(muxc, adapter, max_adapters)
> - + sizeof_priv, GFP_KERNEL);
> + mux_size = struct_size(muxc, adapter, max_adapters);
> + muxc = devm_kzalloc(dev, size_add(mux_size, sizeof_priv), GFP_KERNEL);
> if (!muxc)
> return NULL;
> if (sizeof_priv)
The new variable makes it more readable, but beyond that, do you see any
reason not to just directly compose the calls?
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 774507b54b57..6c481cde6517 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -244,8 +244,10 @@ struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
{
struct i2c_mux_core *muxc;
- muxc = devm_kzalloc(dev, struct_size(muxc, adapter, max_adapters)
- + sizeof_priv, GFP_KERNEL);
+ muxc = devm_kzalloc(dev,
+ size_add(struct_size(muxc, adapter, max_adapters),
+ sizeof_priv),
+ GFP_KERNEL);
if (!muxc)
return NULL;
if (sizeof_priv)
> --
> 2.35.1
>
--
Kees Cook
