Commit fbc0e4e4 authored by Matthew Maurer's avatar Matthew Maurer Committed by Luis Chamberlain
Browse files

module: Factor out elf_validity_cache_index_info 



Centralize .modinfo detection and property validation.

Signed-off-by: default avatarMatthew Maurer <mmaurer@google.com>
Reviewed-by: default avatarSami Tolvanen <samitolvanen@google.com>
Signed-off-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
parent 3c5700ae

kernel/module/main.c

+68 −14
Original line number Diff line number Diff line
@@ -195,6 +195,38 @@ static unsigned int find_sec(const struct load_info *info, const char *name) 
	return 0;

}



/**

 * find_any_unique_sec() - Find a unique section index by name

 * @info: Load info for the module to scan

 * @name: Name of the section we're looking for

 *

 * Locates a unique section by name. Ignores SHF_ALLOC.

 *

 * Return: Section index if found uniquely, zero if absent, negative count

 *         of total instances if multiple were found.

 */

static int find_any_unique_sec(const struct load_info *info, const char *name)

{

	unsigned int idx;

	unsigned int count = 0;

	int i;



	for (i = 1; i < info->hdr->e_shnum; i++) {

		if (strcmp(info->secstrings + info->sechdrs[i].sh_name,

			   name) == 0) {

			count++;

			idx = i;

		}

	}

	if (count == 1) {

		return idx;

	} else if (count == 0) {

		return 0;

	} else {

		return -count;

	}

}



/* Find a module section, or NULL. */

static void *section_addr(const struct load_info *info, const char *name)

{
@@ -1854,6 +1886,39 @@ static int elf_validity_cache_secstrings(struct load_info *info) 
	return 0;

}



/**

 * elf_validity_cache_index_info() - Validate and cache modinfo section

 * @info: Load info to populate the modinfo index on.

 *        Must have &load_info->sechdrs and &load_info->secstrings populated

 *

 * Checks that if there is a .modinfo section, it is unique.

 * Then, it caches its index in &load_info->index.info.

 * Finally, it tries to populate the name to improve error messages.

 *

 * Return: %0 if valid, %-ENOEXEC if multiple modinfo sections were found.

 */

static int elf_validity_cache_index_info(struct load_info *info)

{

	int info_idx;



	info_idx = find_any_unique_sec(info, ".modinfo");



	if (info_idx == 0)

		/* Early return, no .modinfo */

		return 0;



	if (info_idx < 0) {

		pr_err("Only one .modinfo section must exist.\n");

		return -ENOEXEC;

	}



	info->index.info = info_idx;

	/* Try to find a name early so we can log errors with a module name */

	info->name = get_modinfo(info, "name");



	return 0;

}



/*

 * Check userspace passed ELF module against our expectations, and cache

 * useful variables for further processing as we go.
@@ -1880,13 +1945,15 @@ static int elf_validity_cache_copy(struct load_info *info, int flags) 
	Elf_Shdr *shdr;

	int err;

	unsigned int num_mod_secs = 0, mod_idx;

	unsigned int num_info_secs = 0, info_idx;

	unsigned int num_sym_secs = 0, sym_idx;



	err = elf_validity_cache_sechdrs(info);

	if (err < 0)

		return err;

	err = elf_validity_cache_secstrings(info);

	if (err < 0)

		return err;

	err = elf_validity_cache_index_info(info);

	if (err < 0)

		return err;
@@ -1912,24 +1979,11 @@ static int elf_validity_cache_copy(struct load_info *info, int flags) 
				   ".gnu.linkonce.this_module") == 0) {

				num_mod_secs++;

				mod_idx = i;

			} else if (strcmp(info->secstrings + shdr->sh_name,

				   ".modinfo") == 0) {

				num_info_secs++;

				info_idx = i;

			}

			break;

		}

	}



	if (num_info_secs > 1) {

		pr_err("Only one .modinfo section must exist.\n");

		goto no_exec;

	} else if (num_info_secs == 1) {

		/* Try to find a name early so we can log errors with a module name */

		info->index.info = info_idx;

		info->name = get_modinfo(info, "name");

	}



	if (num_sym_secs != 1) {

		pr_warn("%s: module has no symbols (stripped?)\n",

			info->name ?: "(missing .modinfo section or name field)");