/*
* verify the ELF structure of a module
*/
static int module_verify_elf(struct module_verify_data *mvdata)
{
const Elf_Ehdr *hdr = mvdata->hdr;
const Elf_Shdr *section, *section2, *secstop;
const Elf_Rela *relas, *rela, *relastop;
const Elf_Rel *rels, *rel, *relstop;
const Elf_Sym *symbol, *symstop;
size_t size, sssize, *secsize, tmp, tmp2;
long last;
int line;
size = mvdata->size;
mvdata->nsects = hdr->e_shnum;
#define elfcheck(X) \
do { if (unlikely(!(X))) { line = __LINE__; goto elfcheck_error; } } while(0)
#define seccheck(X) \
do { if (unlikely(!(X))) { line = __LINE__; goto seccheck_error; } } while(0)
#define symcheck(X) \
do { if (unlikely(!(X))) { line = __LINE__; goto symcheck_error; } } while(0)
#define relcheck(X) \
do { if (unlikely(!(X))) { line = __LINE__; goto relcheck_error; } } while(0)
#define relacheck(X) \
do { if (unlikely(!(X))) { line = __LINE__; goto relacheck_error; } } while(0)
/* validate the ELF header */
elfcheck(hdr->e_ehsize < size);
elfcheck(hdr->e_entry == 0);
elfcheck(hdr->e_phoff == 0);
elfcheck(hdr->e_phnum == 0);
elfcheck(hdr->e_shnum < SHN_LORESERVE);
elfcheck(hdr->e_shoff < size);
elfcheck(hdr->e_shoff >= hdr->e_ehsize);
elfcheck((hdr->e_shoff & (sizeof(long) - 1)) == 0);
elfcheck(hdr->e_shstrndx > 0);
elfcheck(hdr->e_shstrndx < hdr->e_shnum);
elfcheck(hdr->e_shentsize == sizeof(Elf_Shdr));
tmp = (size_t) hdr->e_shentsize * (size_t) hdr->e_shnum;
elfcheck(tmp <= size - hdr->e_shoff);
/* allocate a table to hold in-file section sizes */
mvdata->secsizes = kmalloc(hdr->e_shnum * sizeof(size_t), GFP_KERNEL);
if (!mvdata->secsizes)
return -ENOMEM;
memset(mvdata->secsizes, 0, hdr->e_shnum * sizeof(size_t));
/* validate the ELF section headers */
mvdata->sections = mvdata->buffer + hdr->e_shoff;
secstop = mvdata->sections + mvdata->nsects;
sssize = mvdata->sections[hdr->e_shstrndx].sh_size;
elfcheck(sssize > 0);
section = mvdata->sections;
seccheck(section->sh_type == SHT_NULL);
seccheck(section->sh_size == 0);
seccheck(section->sh_offset == 0);
secsize = mvdata->secsizes + 1;
for (section++; section < secstop; secsize++, section++) {
seccheck(section->sh_name < sssize);
seccheck(section->sh_link < hdr->e_shnum);
if (section->sh_entsize > 0)
seccheck(section->sh_size % section->sh_entsize == 0);
seccheck(section->sh_offset >= hdr->e_ehsize);
seccheck(section->sh_offset < size);
/* determine the section's in-file size */
tmp = size - section->sh_offset;
if (section->sh_offset < hdr->e_shoff)
tmp = hdr->e_shoff - section->sh_offset;
for (section2 = mvdata->sections + 1; section2 < secstop; section2++) {
if (section->sh_offset < section2->sh_offset) {
tmp2 = section2->sh_offset - section->sh_offset;
if (tmp2 < tmp)
tmp = tmp2;
}
}
*secsize = tmp;
_debug("Section %ld: %zx bytes at %lx\n",
section - mvdata->sections,
*secsize,
section->sh_offset);
/* perform section type specific checks */
switch (section->sh_type) {
case SHT_NOBITS:
break;
case SHT_REL:
seccheck(section->sh_entsize == sizeof(Elf_Rel));
goto more_rel_checks;
case SHT_RELA:
seccheck(section->sh_entsize == sizeof(Elf_Rela));
more_rel_checks:
seccheck(section->sh_info > 0);
seccheck(section->sh_info < hdr->e_shnum);
goto more_sec_checks;
case SHT_SYMTAB:
seccheck(section->sh_entsize == sizeof(Elf_Sym));
goto more_sec_checks;
default:
more_sec_checks:
/* most types of section must be contained entirely
* within the file */
seccheck(section->sh_size <= *secsize);
break;
}
}
/* validate the ELF section names */
section = &mvdata->sections[hdr->e_shstrndx];
seccheck(section->sh_offset != hdr->e_shoff);
mvdata->secstrings = mvdata->buffer + section->sh_offset;
last = -1;
for (section = mvdata->sections + 1; section < secstop; section++) {
const char *secname;
tmp = sssize - section->sh_name;
secname = mvdata->secstrings + section->sh_name;
seccheck(secname[0] != 0);
if (section->sh_name > last)
last = section->sh_name;
}
if (last > -1) {
tmp = sssize - last;
elfcheck(memchr(mvdata->secstrings + last, 0, tmp) != NULL);
}
/* look for various sections in the module */
for (section = mvdata->sections + 1; section < secstop; section++) {
switch (section->sh_type) {
case SHT_SYMTAB:
if (strcmp(mvdata->secstrings + section->sh_name,
".symtab") == 0
) {
seccheck(mvdata->symbols == NULL);
mvdata->symbols =
mvdata->buffer + section->sh_offset;
mvdata->nsyms =
section->sh_size / sizeof(Elf_Sym);
seccheck(section->sh_size > 0);
}
break;
case SHT_STRTAB:
if (strcmp(mvdata->secstrings + section->sh_name,
".strtab") == 0
) {
seccheck(mvdata->strings == NULL);
mvdata->strings =
mvdata->buffer + section->sh_offset;
sssize = mvdata->nstrings = section->sh_size;
seccheck(section->sh_size > 0);
}
break;
}
}
if (!mvdata->symbols) {
printk("Couldn't locate module symbol table\n");
goto format_error;
}
if (!mvdata->strings) {
printk("Couldn't locate module strings table\n");
goto format_error;
}
/* validate the symbol table */
symstop = mvdata->symbols + mvdata->nsyms;
symbol = mvdata->symbols;
symcheck(ELF_ST_TYPE(symbol[0].st_info) == STT_NOTYPE);
symcheck(symbol[0].st_shndx == SHN_UNDEF);
symcheck(symbol[0].st_value == 0);
symcheck(symbol[0].st_size == 0);
last = -1;
for (symbol++; symbol < symstop; symbol++) {
symcheck(symbol->st_name < sssize);
if (symbol->st_name > last)
last = symbol->st_name;
symcheck(symbol->st_shndx < mvdata->nsects ||
symbol->st_shndx >= SHN_LORESERVE);
}
if (last > -1) {
tmp = sssize - last;
elfcheck(memchr(mvdata->strings + last, 0, tmp) != NULL);
}
/* validate each relocation table as best we can */
for (section = mvdata->sections + 1; section < secstop; section++) {
section2 = mvdata->sections + section->sh_info;
switch (section->sh_type) {
case SHT_REL:
rels = mvdata->buffer + section->sh_offset;
relstop = mvdata->buffer + section->sh_offset + section->sh_size;
for (rel = rels; rel < relstop; rel++) {
relcheck(rel->r_offset < section2->sh_size);
relcheck(ELF_R_SYM(rel->r_info) < mvdata->nsyms);
}
break;
case SHT_RELA:
relas = mvdata->buffer + section->sh_offset;
relastop = mvdata->buffer + section->sh_offset + section->sh_size;
for (rela = relas; rela < relastop; rela++) {
relacheck(rela->r_offset < section2->sh_size);
relacheck(ELF_R_SYM(rela->r_info) < mvdata->nsyms);
}
break;
default:
break;
}
}
_debug("ELF okay\n");
return 0;
elfcheck_error:
printk("Verify ELF error (assertion %d)\n", line);
goto format_error;
seccheck_error:
printk("Verify ELF error [sec %ld] (assertion %d)\n",
(long)(section - mvdata->sections), line);
goto format_error;
symcheck_error:
printk("Verify ELF error [sym %ld] (assertion %d)\n",
(long)(symbol - mvdata->symbols), line);
goto format_error;
relcheck_error:
printk("Verify ELF error [sec %ld rel %ld] (assertion %d)\n",
(long)(section - mvdata->sections),
(long)(rel - rels), line);
goto format_error;
relacheck_error:
printk("Verify ELF error [sec %ld rela %ld] (assertion %d)\n",
(long)(section - mvdata->sections),
(long)(rela - relas), line);
goto format_error;
format_error:
return -ELIBBAD;
} /* end module_verify_elf() */
int main(int argc, char **argv)
{
int c, opt = 0;
char *optf;
int fd;
ssize_t l;
optf = NULL;
opterr = 0;
while ((c = getopt(argc, argv, "qrwd")) != -1) {
switch (c) {
case 'r': ifopt; opt = OPT_READ; break;
case 'w': ifopt; opt = OPT_WRITE; break;
case 'd': ifopt; opt = OPT_REMOVE; break;
case 'q': quiet = 1; break;
default: usage(); break;
}
}
optf = *(argv+optind);
if (!optf) usage();
/* sanity checks */
if (!seccheck(optf)) {
errno = EACCES;
xerror(optf);
}
snprintf(B, sizeof(B)-1, "%s/%s", CONFTOOL_BASE, optf);
if (opt == OPT_REMOVE) {
if (unlink(B) == -1) xerror(B);
return 0;
}
fd = open(B, opt == OPT_WRITE ? O_WRONLY | O_TRUNC | O_CREAT : O_RDONLY, 0666);
if (fd == -1) xerror(B);
zerob();
if (!opt || opt == OPT_READ) {
l = read(fd, B, sizeof(B));
if (l) write(1, B, l);
}
else if (opt == OPT_WRITE) {
int x = 1;
l = 0;
if (*(argv+optind+x)) {
while (*(argv+optind+x)) {
l += strlen(*(argv+optind+x));
strncat(B, *(argv+optind+x), sizeof(B)-1-l);
l++; strncat(B, " ", sizeof(B)-1-l);
x++;
}
*(B+l-1) = '\n';
write(fd, B, l);
}
}
close(fd);
return 0;
}
