From: Viresh Kumar <viresh.kumar@linaro.org>
To: Fabien Parent <fabien.parent@linaro.org>
Cc: ilia.lin@kernel.org, agross@kernel.org,
bjorn.andersson@linaro.org, rafael@kernel.org,
linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] cpufreq: qcom: fix writes in read-only memory region
Date: Mon, 10 Oct 2022 11:30:34 +0530 [thread overview]
Message-ID: <20221010060034.wgs7w4onkadoseeb@vireshk-i7> (raw)
In-Reply-To: <20221001171027.2101923-3-fabien.parent@linaro.org>
On 01-10-22, 19:10, Fabien Parent wrote:
> This commit fixes a kernel oops because of a write in some read-only memory:
>
> [ 9.068287] Unable to handle kernel write to read-only memory at virtual address ffff800009240ad8
> ..snip..
> [ 9.138790] Internal error: Oops: 9600004f [#1] PREEMPT SMP
> ..snip..
> [ 9.269161] Call trace:
> [ 9.276271] __memcpy+0x5c/0x230
> [ 9.278531] snprintf+0x58/0x80
> [ 9.282002] qcom_cpufreq_msm8939_name_version+0xb4/0x190
> [ 9.284869] qcom_cpufreq_probe+0xc8/0x39c
> ..snip..
>
> The following line defines a pointer that point to a char buffer stored
> in read-only memory:
>
> char *pvs_name = PVS_NAME;
>
> This pointer is meant to hold a template "speedXX-pvsXX-vXX" where the
> XX values get overridden by the qcom_cpufreq_krait_name_version function. Since
> the template is actually stored in read-only memory, when the function
> executes the following call we get an oops:
>
> snprintf(*pvs_name, sizeof(PVS_NAME), "speed%d-pvs%d-v%d",
> speed, pvs, pvs_ver);
>
> To fix this issue, we instead store the template name onto the stack by
> using the following syntax:
>
> char pvs_name_buffer[] = PVS_NAME;
>
> Because the `pvs_name` needs to be able to be assigned to NULL, the
> template buffer is stored in the pvs_name_template and not under the
> pvs_name variable.
>
> Signed-off-by: Fabien Parent <fabien.parent@linaro.org>
No Fixes or Cc:Stable for this ? This looks like a bug fix and this
should be sent before patch 2/3 so it can be back ported properly.
> ---
> drivers/cpufreq/qcom-cpufreq-nvmem.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/qcom-cpufreq-nvmem.c b/drivers/cpufreq/qcom-cpufreq-nvmem.c
> index 64ce077a4848..3e097262f612 100644
> --- a/drivers/cpufreq/qcom-cpufreq-nvmem.c
> +++ b/drivers/cpufreq/qcom-cpufreq-nvmem.c
> @@ -269,7 +269,8 @@ static int qcom_cpufreq_probe(struct platform_device *pdev)
> struct nvmem_cell *speedbin_nvmem;
> struct device_node *np;
> struct device *cpu_dev;
> - char *pvs_name = PVS_NAME_TEMPLATE;
> + char pvs_name_buffer[] = PVS_NAME_TEMPLATE;
> + char *pvs_name = pvs_name_buffer;
> unsigned cpu;
> const struct of_device_id *match;
> int ret;
> --
> 2.37.2
--
viresh
next prev parent reply other threads:[~2022-10-10 6:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-01 17:10 [PATCH 1/3] cpufreq: qcom: fix memory leak in error path Fabien Parent
2022-10-01 17:10 ` [PATCH 2/3] cpufreq: qcom: pass pvs_name size along with its buffer Fabien Parent
2022-10-10 5:52 ` Viresh Kumar
2022-10-10 6:01 ` Viresh Kumar
2022-10-01 17:10 ` [PATCH 3/3] cpufreq: qcom: fix writes in read-only memory region Fabien Parent
2022-10-10 6:00 ` Viresh Kumar [this message]
2022-10-10 5:55 ` [PATCH 1/3] cpufreq: qcom: fix memory leak in error path Viresh Kumar
2022-10-10 6:02 ` Viresh Kumar
2022-10-15 12:57 ` Fabien Parent
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