Re: [PATCH] i2c: mux: harden i2c_mux_alloc() against integer overflows

Peter Rosin
2022-09-15T13:37:07Z

Hi Dan,

2022-09-15 at 13:30, 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.

Indeed. Nice catch!

> Fixes: 1f3b69b6b939 ("i2c: mux: Use struct_size() in devm_kzalloc()")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Acked-by: Peter Rosin <peda@axentia.se>

Cheers,
Peter

> ---
> 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)