Re: [PATCH] clk: clk-loongson2: Fix potential buffer overflow in flexible-array member access
From: Stephen Boyd
Date: Thu Nov 14 2024 - 20:35:53 EST
Quoting Gustavo A. R. Silva (2024-11-14 15:55:16)
> Flexible-array member `hws` in `struct clk_hw_onecell_data` is annotated
> with the `counted_by()` attribute. This means that when memory is
> allocated for this array, the _counter_, which in this case is member
> `num` in the flexible structure, should be set to the maximum number of
> elements the flexible array can contain, or fewer.
>
> In this case, the total number of elements for the flexible array is
> determined by variable `clks_num` when allocating heap space via
> `devm_kzalloc()`, as shown below:
>
> 289 struct loongson2_clk_provider *clp;
> ...
> 296 for (p = data; p->name; p++)
> 297 clks_num++;
> 298
> 299 clp = devm_kzalloc(dev, struct_size(clp, clk_data.hws, clks_num),
> 300 GFP_KERNEL);
>
> So, `clp->clk_data.num` should be set to `clks_num` or less, and not
> exceed `clks_num`, as is currently the case. Otherwise, if data is
> written into `clp->clk_data.hws[clks_num]`, the instrumentation
> provided by the compiler won't detect the overflow, leading to a
> memory corruption bug at runtime.
>
> Fix this issue by setting `clp->clk_data.num` to `clks_num`.
>
> Fixes: 9796ec0bd04b ("clk: clk-loongson2: Refactor driver for adding new platforms")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> ---
Applied to clk-next