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SubjectRe: [PATCH] Ban module license tag string termination trick
On Thu, 1 Feb 2007 22:20:09 +0100 (MET) Jan Engelhardt wrote:

> ___The kernel patch___
>
> Just a few notes here.
>
>
> Comments welcome.

Good idea.

A diffstat summary would have been nice.
(See Documentation/SubmittingPatches)

Use a space between "if" and "(" below (multiple times):
see Documentation/CodingStyle.


> Index: linux-2.6.20-rc7/kernel/module.c
> ===================================================================
> --- linux-2.6.20-rc7.orig/kernel/module.c
> +++ linux-2.6.20-rc7/kernel/module.c
> @@ -1389,10 +1389,21 @@ static void layout_sections(struct modul
> }
> }
>
> -static void set_license(struct module *mod, const char *license)
> +static int set_license(struct module *mod, Elf_Shdr *sechdr)
> {
> - if (!license)
> - license = "unspecified";
> + const char *license = "unspecified";
> +
> + if(sechdr != NULL) {
> + license = (const char *)sechdr->sh_addr;
> +
> + /* Allow both non-terminated strings and NUL-terminated
> + strings, as long as no string termination trick is done. */
> + if(strnlen(license, sechdr->sh_size) + 1 != sechdr->sh_size) {
> + printk(KERN_WARNING "Module \"%s\" has invalid "
> + ".modlicense section\n", mod->name);
> + return -EINVAL;
> + }
> + }
>
> if (!license_is_gpl_compatible(license)) {
> if (!(tainted & TAINT_PROPRIETARY_MODULE))
> @@ -1400,6 +1411,8 @@ static void set_license(struct module *m
> "kernel.\n", mod->name, license);
> add_taint_module(mod, TAINT_PROPRIETARY_MODULE);
> }
> +
> + return 0;
> }
>
> /* Parse tag=value strings from .modinfo section */
> @@ -1549,6 +1562,7 @@ static struct module *load_module(void _
> unsigned int modindex;
> unsigned int obsparmindex;
> unsigned int infoindex;
> + unsigned int license_index;
> unsigned int gplindex;
> unsigned int crcindex;
> unsigned int gplcrcindex;
> @@ -1653,6 +1667,7 @@ static struct module *load_module(void _
> obsparmindex = find_sec(hdr, sechdrs, secstrings, "__obsparm");
> versindex = find_sec(hdr, sechdrs, secstrings, "__versions");
> infoindex = find_sec(hdr, sechdrs, secstrings, ".modinfo");
> + license_index = find_sec(hdr, sechdrs, secstrings, ".modlicense");
> pcpuindex = find_pcpusec(hdr, sechdrs, secstrings);
> #ifdef ARCH_UNWIND_SECTION_NAME
> unwindex = find_sec(hdr, sechdrs, secstrings, ARCH_UNWIND_SECTION_NAME);
> @@ -1660,6 +1675,8 @@ static struct module *load_module(void _
>
> /* Don't keep modinfo section */
> sechdrs[infoindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
> + if(license_index)
> + sechdrs[license_index].sh_flags &= ~SHF_ALLOC;
> #ifdef CONFIG_KALLSYMS
> /* Keep symbol and string tables for decoding later. */
> sechdrs[symindex].sh_flags |= SHF_ALLOC;
> @@ -1769,7 +1786,10 @@ static struct module *load_module(void _
> module_unload_init(mod);
>
> /* Set up license info based on the info section */
> - set_license(mod, get_modinfo(sechdrs, infoindex, "license"));
> + err = set_license(mod, (license_index != 0) ?
> + &sechdrs[license_index] : NULL);
> + if(err)
> + goto cleanup;
>
> if (strcmp(mod->name, "ndiswrapper") == 0)
> add_taint(TAINT_PROPRIETARY_MODULE);


---
~Randy
-
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