Re: [PATCH] cpufreq: amd-pstate-ut: fix null pointer dereference

[Viresh Kumar]

On 14-07-26, 15:59, Qianheng Peng wrote:
> The crash issue may occur when insmod amd_pstate_ut modules.
> 
>    amd_pstate_ut: 1    amd_pstate_ut_acpi_cpc_valid  success!
>    amd_pstate_ut: 2    amd_pstate_ut_check_enabled   success!
>    BUG: kernel NULL pointer dereference, address: 0000000000000080
>    #PF: supervisor read access in kernel mode
>    #PF: error_code(0x0000) - not-present page
>    PGD 0 P4D 0
>    Oops: 0000 [#1] SMP NOPTI
>    CPU: 0 PID: 20300 Comm: modprobe
>    Kdump: loaded Tainted: G O 6.6.0-0010.rc1.ctl4.x86_64 #1
>    Hardware name: FiberHome R2200 V5/Xeon Boards, BIOS 3.1a 02/24/2020
>    RIP: 0010:amd_pstate_ut_check_perf+0x141/0x280 [amd_pstate_ut]
>    Call Trace:
>     <TASK>
>     amd_pstate_ut_init+0x1b/0xff0 [amd_pstate_ut]
>     ? __pfx_amd_pstate_ut_init+0x10/0x10 [amd_pstate_ut]
>     do_one_initcall+0x42/0x2e0
>     ? kmalloc_trace+0x26/0x90
>     do_init_module+0x60/0x240
>     __se_sys_init_module+0x185/0x1c0
>     do_syscall_64+0x62/0x190
>     entry_SYSCALL_64_after_hwframe+0x76/0x7e
>     </TASK>
> 
> Add invalidation check of cpudata in amd_pstate_ut_check_perf() and
> amd_pstate_ut_check_freq() to avoid unpredicated null pointer dereference.
> 
> Fixes: 14eb1c96e3a3 ("cpufreq: amd-pstate: Add test module for amd-pstate driver")
> Suggested-by: Li Xiong <xiongl24@xxxxxxxxxxxxxxx>
> Suggested-by: Xibo Wang <wangxb12@xxxxxxxxxxxxxxx>
> Signed-off-by: Qianheng Peng <pengqh1@xxxxxxxxxxxxxxx>
> ---
>  drivers/cpufreq/amd-pstate-ut.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate-ut.c b/drivers/cpufreq/amd-pstate-ut.c
> index 735b29f..3b24260 100644
> --- a/drivers/cpufreq/amd-pstate-ut.c
> +++ b/drivers/cpufreq/amd-pstate-ut.c
> @@ -157,6 +157,10 @@ static int amd_pstate_ut_check_perf(u32 index)
>  		if (!policy)
>  			continue;
>  		cpudata = policy->driver_data;
> +		if (!cpudata) {
> +			pr_err("%s driver_data of %s is empty!\n", __func__, policy->kobj.name);

You can use kobject_name(), but I wonder why print kobj name here ? Other
drivers just print policy->cpu normally and that is sufficient.

-- 
viresh