netdev - Re: [PATCH v4 -next 13/15] x86: vdso: move the sysctl to arch/x86/entry/vdso/vdso32-setup.c

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Message-ID: <5b7530d9-a593-4365-718f-afdd46bdcb31@huawei.com>
Date: Mon, 30 Dec 2024 11:02:38 +0800
From: yukaixiong <yukaixiong@...wei.com>
To: Brian Gerst <brgerst@...il.com>
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Subject: Re: [PATCH v4 -next 13/15] x86: vdso: move the sysctl to
 arch/x86/entry/vdso/vdso32-setup.c



On 2024/12/30 7:05, Brian Gerst wrote:
> On Sat, Dec 28, 2024 at 10:17 AM Kaixiong Yu <yukaixiong@...wei.com> wrote:
>> When CONFIG_X86_32 is defined and CONFIG_UML is not defined,
>> vdso_enabled belongs to arch/x86/entry/vdso/vdso32-setup.c.
>> So, move it into its own file.
>>
>> Before this patch, vdso_enabled was allowed to be set to
>> a value exceeding 1 on x86_32 architecture. After this patch is
>> applied, vdso_enabled is not permitted to set the value more than 1.
>> It does not matter, because according to the function load_vdso32(),
>> only vdso_enabled is set to 1, VDSO would be enabled. Other values
>> all mean "disabled". The same limitation could be seen in the
>> function vdso32_setup().
>>
>> Signed-off-by: Kaixiong Yu <yukaixiong@...wei.com>
>> Reviewed-by: Kees Cook <kees@...nel.org>
>> ---
>> v4:
>>   - const qualify struct ctl_table vdso_table
>> ---
>> ---
>>   arch/x86/entry/vdso/vdso32-setup.c | 16 +++++++++++-----
>>   kernel/sysctl.c                    |  8 +-------
>>   2 files changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/x86/entry/vdso/vdso32-setup.c b/arch/x86/entry/vdso/vdso32-setup.c
>> index 76e4e74f35b5..f71625f99bf9 100644
>> --- a/arch/x86/entry/vdso/vdso32-setup.c
>> +++ b/arch/x86/entry/vdso/vdso32-setup.c
>> @@ -51,15 +51,17 @@ __setup("vdso32=", vdso32_setup);
>>   __setup_param("vdso=", vdso_setup, vdso32_setup, 0);
>>   #endif
>>
>> -#ifdef CONFIG_X86_64
>>
>>   #ifdef CONFIG_SYSCTL
>> -/* Register vsyscall32 into the ABI table */
>>   #include <linux/sysctl.h>
>>
>> -static struct ctl_table abi_table2[] = {
>> +static const struct ctl_table vdso_table[] = {
>>          {
>> +#ifdef CONFIG_X86_64
>>                  .procname       = "vsyscall32",
>> +#elif (defined(CONFIG_X86_32) && !defined(CONFIG_UML))
> vdso32-setup,.c is not used when building UML, so this can be reduced
> to "#else".
I will take your advice.

Thanks.
>> +               .procname       = "vdso_enabled",
>> +#endif
>>                  .data           = &vdso32_enabled,
>>                  .maxlen         = sizeof(int),
>>                  .mode           = 0644,
>> @@ -71,10 +73,14 @@ static struct ctl_table abi_table2[] = {
>>
>>   static __init int ia32_binfmt_init(void)
>>   {
>> -       register_sysctl("abi", abi_table2);
>> +#ifdef CONFIG_X86_64
>> +       /* Register vsyscall32 into the ABI table */
>> +       register_sysctl("abi", vdso_table);
>> +#elif (defined(CONFIG_X86_32) && !defined(CONFIG_UML))
> Same as above.
>
>
I will take your advice.

Thanks.
>> +       register_sysctl_init("vm", vdso_table);
>> +#endif
>>          return 0;
>>   }
>>   __initcall(ia32_binfmt_init);
>>   #endif /* CONFIG_SYSCTL */
>>
>> -#endif /* CONFIG_X86_64 */
>
> Brian Gerst
> .
>