Re: [m-i-t part] Ban module license tag string termination trick

From: Jan Engelhardt
Date: Thu Feb 01 2007 - 16:29:56 EST


Hello Ccs, hello list,



The m-i-t list subscription is foobared today, so no Cc. To compensate,
Jon has been Cced.


jengelh wrote:
>
>Proposed patch to prohibit loading modules that use early C string
>termination ("GPL\0 for nothing, folks!") to trick the kernel believing
>it is loading a GPL driver.
>[...]
>To work against this problem, we must store the length of the actual
>string as the compiler knows it. This will become really cumbersome if
>implemented as a new tag inside the modinfo section. Hence I chose the
>way of adding a new section called ".modlicense". The length of the new
>section's header will automatically be the string length [including
>trailing NUL]. The module loading code then just has to compare the
>section length with the string length as returned by strlen().
>[...]
>A separate patch is required for module-init-tools (m-i-t) to make the
>"modinfo" userspace utility understand the new modlicense section. I do
>not think the world will explode if someone runs an unpatched m-i-t with
>a patched kernel.

Signed-off-by: Jan Engelhardt <jengelh@xxxxxx>

# modlicense-MIT.diff
Index: module-init-tools-3.2.2/modinfo.c
===================================================================
--- module-init-tools-3.2.2.orig/modinfo.c
+++ module-init-tools-3.2.2/modinfo.c
@@ -376,12 +376,22 @@ int main(int argc, char *argv[])
}

info = get_section(mod, modulesize, &infosize, ".modinfo");
- if (!info)
- continue;
- if (field)
- print_tag(field, info, infosize, filename, sep);
- else
- print_all(info, infosize, filename, sep);
+ if (info) {
+ if (field)
+ print_tag(field, info, infosize, filename, sep);
+ else
+ print_all(info, infosize, filename, sep);
+ }
+
+ info = get_section(mod, modulesize, &infosize, ".modlicense");
+ if(info != NULL && strnlen(info, infosize) + 1 == infosize) {
+ if(field != NULL && streq(field, "license"))
+ printf("%s%c", (const char *)info, sep);
+ else
+ printf("%-16s%s%c", "license:",
+ (const char *)info, sep);
+ }
+
free(filename);
}
return ret;
#<EOF>
-
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