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 <[email protected]>
---
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
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 <[email protected]>
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