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

[Brian Gerst]

On Sat, Dec 28, 2024 at 10:17 AM Kaixiong Yu <yukaixiong@xxxxxxxxxx> 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@xxxxxxxxxx>
> Reviewed-by: Kees Cook <kees@xxxxxxxxxx>
> ---
> 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".

> +               .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.



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


Brian Gerst