linux-kernel - Re: [PATCH] clk: clk-loongson2: Fix potential buffer overflow in flexible-array member access

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Message-ID: <ed2e1be4be4716b2c436a163ae40ef07.sboyd@kernel.org>
Date: Thu, 14 Nov 2024 17:35:41 -0800
From: Stephen Boyd <sboyd@...nel.org>
To: Binbin Zhou <zhoubinbin@...ngson.cn>, Gustavo A. R. Silva <gustavoars@...nel.org>, Huacai Chen <chenhuacai@...nel.org>, Michael Turquette <mturquette@...libre.com>, Yinbo Zhu <zhuyinbo@...ngson.cn>
Cc: linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, Gustavo A. R. Silva <gustavoars@...nel.org>, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] clk: clk-loongson2: Fix potential buffer overflow in flexible-array member access

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@...r.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---

Applied to clk-next