Re: [PATCH] module: check vermagic match exactly when load modules

From: Rusty Russell
Date: Wed Dec 09 2015 - 23:54:46 EST


Xie XiuQi <xiexiuqi@xxxxxxxxxx> writes:
> Usually, checking kernel version will be ignore when loading
> modules if CONFIG_MODVERSIONS option is enable. This could
> potentially lead to a mismatch with the running kernel.
>
> With this option, we prevent to load the modules which vermagic
> is not match exactly with the running kernel.
>
> It could be set to N by default.

Hi Xie!

I don't understand this patch. The purpose of
CONFIG_MODVERSIONS is so that you can combine modules from different
kernel versions. If you don't want to do that, I suggest not setting
CONFIG_MODVERSIONS.

Cheers,
Rusty.

>
> Signed-off-by: Xie XiuQi <xiexiuqi@xxxxxxxxxx>
> ---
> init/Kconfig | 11 +++++++++++
> kernel/module.c | 2 ++
> 2 files changed, 13 insertions(+)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index c24b6f7..ce9c23e 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1889,6 +1889,17 @@ config MODVERSIONS
> make them incompatible with the kernel you are running. If
> unsure, say N.
>
> +config MODULE_VERMAGIC_FORCE
> + bool "Require vermagic match exactly"
> + default n
> + depends on MODVERSIONS
> + help
> + Usually, checking kernel version will be ignore when loading
> + modules if CONFIG_MODVERSIONS option is enable. This could
> + potentially lead to a mismatch with the running kernel.
> + With this option, we prevent to load the modules which vermagic
> + is not match exactly with the running kernel. If unsure, say N.
> +
> config MODULE_SRCVERSION_ALL
> bool "Source checksum for all modules"
> help
> diff --git a/kernel/module.c b/kernel/module.c
> index 8f051a1..cf350d5 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1350,10 +1350,12 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
> static inline int same_magic(const char *amagic, const char *bmagic,
> bool has_crcs)
> {
> +#ifndef CONFIG_MODULE_VERMAGIC_FORCE
> if (has_crcs) {
> amagic += strcspn(amagic, " ");
> bmagic += strcspn(bmagic, " ");
> }
> +#endif
> return strcmp(amagic, bmagic) == 0;
> }
> #else
> --
> 1.8.3.1
>
> --
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