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Date: Tue, 21 Jul 2020 12:10:07 +0200
From: Luca Ceresoli <luca@...aceresoli.net>
To: Colin King <colin.king@...onical.com>,
Marek Vasut <marek.vasut@...il.com>,
Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>,
Adam Ford <aford173@...il.com>, linux-clk@...r.kernel.org
Cc: kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] clk: vc5: fix use of memory after it has been
kfree'd
Hi Colin,
On 25/06/20 15:27, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
>
> There are a several places where printing an error message of
> init.name occurs after init.name has been kfree'd. Also the failure
> message is duplicated each time in the code. Fix this by adding
> a registration error failure path for these cases, moving the
> duplicated error messages to one common point and kfree'ing init.name
> only after it has been used.
>
> Changes also shrink the object code size by 171 bytes (x86-64, gcc 9.3):
>
> Before:
> text data bss dec hex filename
> 21057 3960 64 25081 61f9 drivers/clk/clk-versaclock5.o
>
> After:
> text data bss dec hex filename
> 20886 3960 64 24910 614e drivers/clk/clk-versaclock5.o
>
> Addresses-Coverity: ("Use after free")
> Fixes: f491276a5168 ("clk: vc5: Allow Versaclock driver to support multiple instances")
>
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
Woah, good catch!
> ---
> drivers/clk/clk-versaclock5.c | 51 +++++++++++++----------------------
> 1 file changed, 19 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/clk/clk-versaclock5.c b/drivers/clk/clk-versaclock5.c
> index 9a5fb3834b9a..1d8ee4b8b1f5 100644
> --- a/drivers/clk/clk-versaclock5.c
> +++ b/drivers/clk/clk-versaclock5.c
> @@ -882,11 +882,9 @@ static int vc5_probe(struct i2c_client *client, const struct i2c_device_id *id)
> init.parent_names = parent_names;
> vc5->clk_mux.init = &init;
> ret = devm_clk_hw_register(&client->dev, &vc5->clk_mux);
> + if (ret)
> + goto err_clk_register;
> kfree(init.name); /* clock framework made a copy of the name */
> - if (ret) {
> - dev_err(&client->dev, "unable to register %s\n", init.name);
> - goto err_clk;
> - }
>
> if (vc5->chip_info->flags & VC5_HAS_PFD_FREQ_DBL) {
> /* Register frequency doubler */
> @@ -900,12 +898,9 @@ static int vc5_probe(struct i2c_client *client, const struct i2c_device_id *id)
> init.num_parents = 1;
> vc5->clk_mul.init = &init;
> ret = devm_clk_hw_register(&client->dev, &vc5->clk_mul);
> + if (ret)
> + goto err_clk_register;
> kfree(init.name); /* clock framework made a copy of the name */
> - if (ret) {
> - dev_err(&client->dev, "unable to register %s\n",
> - init.name);
> - goto err_clk;
> - }
> }
>
> /* Register PFD */
> @@ -921,11 +916,9 @@ static int vc5_probe(struct i2c_client *client, const struct i2c_device_id *id)
> init.num_parents = 1;
> vc5->clk_pfd.init = &init;
> ret = devm_clk_hw_register(&client->dev, &vc5->clk_pfd);
> + if (ret)
> + goto err_clk_register;
> kfree(init.name); /* clock framework made a copy of the name */
> - if (ret) {
> - dev_err(&client->dev, "unable to register %s\n", init.name);
> - goto err_clk;
> - }
>
> /* Register PLL */
> memset(&init, 0, sizeof(init));
> @@ -939,11 +932,9 @@ static int vc5_probe(struct i2c_client *client, const struct i2c_device_id *id)
> vc5->clk_pll.vc5 = vc5;
> vc5->clk_pll.hw.init = &init;
> ret = devm_clk_hw_register(&client->dev, &vc5->clk_pll.hw);
> + if (ret)
> + goto err_clk_register;
> kfree(init.name); /* clock framework made a copy of the name */
> - if (ret) {
> - dev_err(&client->dev, "unable to register %s\n", init.name);
> - goto err_clk;
> - }
>
> /* Register FODs */
> for (n = 0; n < vc5->chip_info->clk_fod_cnt; n++) {
> @@ -960,12 +951,9 @@ static int vc5_probe(struct i2c_client *client, const struct i2c_device_id *id)
> vc5->clk_fod[n].vc5 = vc5;
> vc5->clk_fod[n].hw.init = &init;
> ret = devm_clk_hw_register(&client->dev, &vc5->clk_fod[n].hw);
> + if (ret)
> + goto err_clk_register;
> kfree(init.name); /* clock framework made a copy of the name */
> - if (ret) {
> - dev_err(&client->dev, "unable to register %s\n",
> - init.name);
> - goto err_clk;
> - }
> }
>
> /* Register MUX-connected OUT0_I2C_SELB output */
> @@ -981,11 +969,9 @@ static int vc5_probe(struct i2c_client *client, const struct i2c_device_id *id)
> vc5->clk_out[0].vc5 = vc5;
> vc5->clk_out[0].hw.init = &init;
> ret = devm_clk_hw_register(&client->dev, &vc5->clk_out[0].hw);
> - kfree(init.name); /* clock framework made a copy of the name */
> - if (ret) {
> - dev_err(&client->dev, "unable to register %s\n", init.name);
> - goto err_clk;
> - }
> + if (ret)
> + goto err_clk_register;
> + kfree(init.name); /* clock framework made a copy of the name */
>
> /* Register FOD-connected OUTx outputs */
> for (n = 1; n < vc5->chip_info->clk_out_cnt; n++) {
> @@ -1008,17 +994,15 @@ static int vc5_probe(struct i2c_client *client, const struct i2c_device_id *id)
> vc5->clk_out[n].vc5 = vc5;
> vc5->clk_out[n].hw.init = &init;
> ret = devm_clk_hw_register(&client->dev, &vc5->clk_out[n].hw);
> + if (ret)
> + goto err_clk_register;
> kfree(init.name); /* clock framework made a copy of the name */
> - if (ret) {
> - dev_err(&client->dev, "unable to register %s\n",
> - init.name);
> - goto err_clk;
> - }
>
> /* Fetch Clock Output configuration from DT (if specified) */
> ret = vc5_get_output_config(client, &vc5->clk_out[n]);
> if (ret)
> goto err_clk;
> +
> }
Stray newline. With it possibly fixed:
Reviewed-by: Luca Ceresoli <luca@...aceresoli.net>
--
Luca
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