From 7fd982f394c42f25a73fe9dfbf1e6b11fa26b40a Mon Sep 17 00:00:00 2001 From: Shuah Khan Date: Fri, 15 Oct 2021 14:57:40 -0600 Subject: module: change to print useful messages from elf_validity_check() elf_validity_check() checks ELF headers for errors and ELF Spec. compliance and if any of them fail it returns -ENOEXEC from all of these error paths. Almost all of them don't print any messages. When elf_validity_check() returns an error, load_module() prints an error message without error code. It is hard to determine why the module ELF structure is invalid, even if load_module() prints the error code which is -ENOEXEC in all of these cases. Change to print useful error messages from elf_validity_check() to clearly say what went wrong and why the ELF validity checks failed. Remove the load_module() error message which is no longer needed. This patch includes changes to fix build warns on 32-bit platforms: warning: format '%llu' expects argument of type 'long long unsigned int', but argument 3 has type 'Elf32_Off' {aka 'unsigned int'} Reported-by: kernel test robot Signed-off-by: Shuah Khan Signed-off-by: Luis Chamberlain --- kernel/module.c | 75 +++++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 54 insertions(+), 21 deletions(-) diff --git a/kernel/module.c b/kernel/module.c index c7ad73807446..84a9141a5e15 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2971,14 +2971,29 @@ static int elf_validity_check(struct load_info *info) Elf_Shdr *shdr, *strhdr; int err; - if (info->len < sizeof(*(info->hdr))) - return -ENOEXEC; + if (info->len < sizeof(*(info->hdr))) { + pr_err("Invalid ELF header len %lu\n", info->len); + goto no_exec; + } - if (memcmp(info->hdr->e_ident, ELFMAG, SELFMAG) != 0 - || info->hdr->e_type != ET_REL - || !elf_check_arch(info->hdr) - || info->hdr->e_shentsize != sizeof(Elf_Shdr)) - return -ENOEXEC; + 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 (info->hdr->e_shentsize != sizeof(Elf_Shdr)) { + pr_err("Invalid ELF section header size\n"); + goto no_exec; + } /* * e_shnum is 16 bits, and sizeof(Elf_Shdr) is @@ -2987,8 +3002,10 @@ static int elf_validity_check(struct load_info *info) */ if (info->hdr->e_shoff >= info->len || (info->hdr->e_shnum * sizeof(Elf_Shdr) > - info->len - info->hdr->e_shoff)) - return -ENOEXEC; + info->len - info->hdr->e_shoff)) { + pr_err("Invalid ELF section header overflow\n"); + goto no_exec; + } info->sechdrs = (void *)info->hdr + info->hdr->e_shoff; @@ -2996,13 +3013,19 @@ static int elf_validity_check(struct load_info *info) * Verify if the section name table index is valid. */ if (info->hdr->e_shstrndx == SHN_UNDEF - || info->hdr->e_shstrndx >= info->hdr->e_shnum) - return -ENOEXEC; + || info->hdr->e_shstrndx >= info->hdr->e_shnum) { + pr_err("Invalid ELF section name index: %d || e_shstrndx (%d) >= e_shnum (%d)\n", + info->hdr->e_shstrndx, info->hdr->e_shstrndx, + info->hdr->e_shnum); + goto no_exec; + } strhdr = &info->sechdrs[info->hdr->e_shstrndx]; err = validate_section_offset(info, strhdr); - if (err < 0) + if (err < 0) { + pr_err("Invalid ELF section hdr(type %u)\n", strhdr->sh_type); return err; + } /* * The section name table must be NUL-terminated, as required @@ -3010,8 +3033,10 @@ static int elf_validity_check(struct load_info *info) * strings in the section safe. */ info->secstrings = (void *)info->hdr + strhdr->sh_offset; - if (info->secstrings[strhdr->sh_size - 1] != '\0') - return -ENOEXEC; + if (info->secstrings[strhdr->sh_size - 1] != '\0') { + pr_err("ELF Spec violation: section name table isn't null terminated\n"); + goto no_exec; + } /* * The code assumes that section 0 has a length of zero and @@ -3019,8 +3044,11 @@ static int elf_validity_check(struct load_info *info) */ if (info->sechdrs[0].sh_type != SHT_NULL || info->sechdrs[0].sh_size != 0 - || info->sechdrs[0].sh_addr != 0) - return -ENOEXEC; + || info->sechdrs[0].sh_addr != 0) { + pr_err("ELF Spec violation: section 0 type(%d)!=SH_NULL or non-zero len or addr\n", + info->sechdrs[0].sh_type); + goto no_exec; + } for (i = 1; i < info->hdr->e_shnum; i++) { shdr = &info->sechdrs[i]; @@ -3030,8 +3058,12 @@ static int elf_validity_check(struct load_info *info) continue; case SHT_SYMTAB: if (shdr->sh_link == SHN_UNDEF - || shdr->sh_link >= info->hdr->e_shnum) - return -ENOEXEC; + || shdr->sh_link >= info->hdr->e_shnum) { + pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= hdr->e_shnum(%d)\n", + shdr->sh_link, shdr->sh_link, + info->hdr->e_shnum); + goto no_exec; + } fallthrough; default: err = validate_section_offset(info, shdr); @@ -3053,6 +3085,9 @@ static int elf_validity_check(struct load_info *info) } return 0; + +no_exec: + return -ENOEXEC; } #define COPY_CHUNK_SIZE (16*PAGE_SIZE) @@ -3944,10 +3979,8 @@ static int load_module(struct load_info *info, const char __user *uargs, * sections. */ err = elf_validity_check(info); - if (err) { - pr_err("Module has invalid ELF structures\n"); + if (err) goto free_copy; - } /* * Everything checks out, so set up the section info -- cgit