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

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

[Xie XiuQi]

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.

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
---
 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

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

[Rusty Russell]

Xie XiuQi <xiexiuqi@huawei.com> 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@huawei.com>
> ---
>  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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