Commit 90f8f312 authored by Matthew Maurer's avatar Matthew Maurer Committed by Luis Chamberlain
Browse files

module: Factor out elf_validity_ehdr 



Factor out verification of the ELF header and document what is checked.

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 f4392216

kernel/module/main.c

+47 −23
Original line number Diff line number Diff line
@@ -1664,6 +1664,50 @@ static int validate_section_offset(const struct load_info *info, Elf_Shdr *shdr) 
	return 0;

}



/**

 * elf_validity_ehdr() - Checks an ELF header for module validity

 * @info: Load info containing the ELF header to check

 *

 * Checks whether an ELF header could belong to a valid module. Checks:

 *

 * * ELF header is within the data the user provided

 * * ELF magic is present

 * * It is relocatable (not final linked, not core file, etc.)

 * * The header's machine type matches what the architecture expects.

 * * Optional arch-specific hook for other properties

 *   - module_elf_check_arch() is currently only used by PPC to check

 *   ELF ABI version, but may be used by others in the future.

 *

 * Return: %0 if valid, %-ENOEXEC on failure.

 */

static int elf_validity_ehdr(const struct load_info *info)

{

	if (info->len < sizeof(*(info->hdr))) {

		pr_err("Invalid ELF header len %lu\n", info->len);

		return -ENOEXEC;

	}

	if (memcmp(info->hdr->e_ident, ELFMAG, SELFMAG) != 0) {

		pr_err("Invalid ELF header magic: != %s\n", ELFMAG);

		return -ENOEXEC;

	}

	if (info->hdr->e_type != ET_REL) {

		pr_err("Invalid ELF header type: %u != %u\n",

		       info->hdr->e_type, ET_REL);

		return -ENOEXEC;

	}

	if (!elf_check_arch(info->hdr)) {

		pr_err("Invalid architecture in ELF header: %u\n",

		       info->hdr->e_machine);

		return -ENOEXEC;

	}

	if (!module_elf_check_arch(info->hdr)) {

		pr_err("Invalid module architecture in ELF header: %u\n",

		       info->hdr->e_machine);

		return -ENOEXEC;

	}

	return 0;

}



/*

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

 * useful variables for further processing as we go.
@@ -1693,30 +1737,10 @@ static int elf_validity_cache_copy(struct load_info *info, int flags) 
	unsigned int num_info_secs = 0, info_idx;

	unsigned int num_sym_secs = 0, sym_idx;



	if (info->len < sizeof(*(info->hdr))) {

		pr_err("Invalid ELF header len %lu\n", info->len);

		goto no_exec;

	}

	err = elf_validity_ehdr(info);

	if (err < 0)

		return err;



	if (memcmp(info->hdr->e_ident, ELFMAG, SELFMAG) != 0) {

		pr_err("Invalid ELF header magic: != %s\n", ELFMAG);

		goto no_exec;

	}

	if (info->hdr->e_type != ET_REL) {

		pr_err("Invalid ELF header type: %u != %u\n",

		       info->hdr->e_type, ET_REL);

		goto no_exec;

	}

	if (!elf_check_arch(info->hdr)) {

		pr_err("Invalid architecture in ELF header: %u\n",

		       info->hdr->e_machine);

		goto no_exec;

	}

	if (!module_elf_check_arch(info->hdr)) {

		pr_err("Invalid module architecture in ELF header: %u\n",

		       info->hdr->e_machine);

		goto no_exec;

	}

	if (info->hdr->e_shentsize != sizeof(Elf_Shdr)) {

		pr_err("Invalid ELF section header size\n");

		goto no_exec;