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qemu/include/hw/elf_ops.h
Stefano Garzarella 41a2635124 elf-ops.h: fix int overflow in load_elf() 
This patch fixes a possible integer overflow when we calculate
the total size of ELF segments loaded.

Reported-by: Coverity (CID 1405299)
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20190910124828.39794-1-sgarzare@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-09-16 12:32:21 +02:00

607 lines
20 KiB
C
Raw Blame History

static void glue(bswap_ehdr, SZ)(struct elfhdr *ehdr)
{
bswap16s(&ehdr->e_type); /* Object file type */
bswap16s(&ehdr->e_machine); /* Architecture */
bswap32s(&ehdr->e_version); /* Object file version */
bswapSZs(&ehdr->e_entry); /* Entry point virtual address */
bswapSZs(&ehdr->e_phoff); /* Program header table file offset */
bswapSZs(&ehdr->e_shoff); /* Section header table file offset */
bswap32s(&ehdr->e_flags); /* Processor-specific flags */
bswap16s(&ehdr->e_ehsize); /* ELF header size in bytes */
bswap16s(&ehdr->e_phentsize); /* Program header table entry size */
bswap16s(&ehdr->e_phnum); /* Program header table entry count */
bswap16s(&ehdr->e_shentsize); /* Section header table entry size */
bswap16s(&ehdr->e_shnum); /* Section header table entry count */
bswap16s(&ehdr->e_shstrndx); /* Section header string table index */
}
static void glue(bswap_phdr, SZ)(struct elf_phdr *phdr)
{
bswap32s(&phdr->p_type); /* Segment type */
bswapSZs(&phdr->p_offset); /* Segment file offset */
bswapSZs(&phdr->p_vaddr); /* Segment virtual address */
bswapSZs(&phdr->p_paddr); /* Segment physical address */
bswapSZs(&phdr->p_filesz); /* Segment size in file */
bswapSZs(&phdr->p_memsz); /* Segment size in memory */
bswap32s(&phdr->p_flags); /* Segment flags */
bswapSZs(&phdr->p_align); /* Segment alignment */
}
static void glue(bswap_shdr, SZ)(struct elf_shdr *shdr)
{
bswap32s(&shdr->sh_name);
bswap32s(&shdr->sh_type);
bswapSZs(&shdr->sh_flags);
bswapSZs(&shdr->sh_addr);
bswapSZs(&shdr->sh_offset);
bswapSZs(&shdr->sh_size);
bswap32s(&shdr->sh_link);
bswap32s(&shdr->sh_info);
bswapSZs(&shdr->sh_addralign);
bswapSZs(&shdr->sh_entsize);
}
static void glue(bswap_sym, SZ)(struct elf_sym *sym)
{
bswap32s(&sym->st_name);
bswapSZs(&sym->st_value);
bswapSZs(&sym->st_size);
bswap16s(&sym->st_shndx);
}
static void glue(bswap_rela, SZ)(struct elf_rela *rela)
{
bswapSZs(&rela->r_offset);
bswapSZs(&rela->r_info);
bswapSZs((elf_word *)&rela->r_addend);
}
static struct elf_shdr *glue(find_section, SZ)(struct elf_shdr *shdr_table,
int n, int type)
{
int i;
for(i=0;i<n;i++) {
if (shdr_table[i].sh_type == type)
return shdr_table + i;
}
return NULL;
}
static int glue(symfind, SZ)(const void *s0, const void *s1)
{
hwaddr addr = *(hwaddr *)s0;
struct elf_sym *sym = (struct elf_sym *)s1;
int result = 0;
if (addr < sym->st_value) {
result = -1;
} else if (addr >= sym->st_value + sym->st_size) {
result = 1;
}
return result;
}
static const char *glue(lookup_symbol, SZ)(struct syminfo *s,
hwaddr orig_addr)
{
struct elf_sym *syms = glue(s->disas_symtab.elf, SZ);
struct elf_sym *sym;
sym = bsearch(&orig_addr, syms, s->disas_num_syms, sizeof(*syms),
glue(symfind, SZ));
if (sym != NULL) {
return s->disas_strtab + sym->st_name;
}
return "";
}
static int glue(symcmp, SZ)(const void *s0, const void *s1)
{
struct elf_sym *sym0 = (struct elf_sym *)s0;
struct elf_sym *sym1 = (struct elf_sym *)s1;
return (sym0->st_value < sym1->st_value)
? -1
: ((sym0->st_value > sym1->st_value) ? 1 : 0);
}
static int glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int must_swab,
int clear_lsb, symbol_fn_t sym_cb)
{
struct elf_shdr *symtab, *strtab, *shdr_table = NULL;
struct elf_sym *syms = NULL;
struct syminfo *s;
int nsyms, i;
char *str = NULL;
shdr_table = load_at(fd, ehdr->e_shoff,
sizeof(struct elf_shdr) * ehdr->e_shnum);
if (!shdr_table)
return -1;
if (must_swab) {
for (i = 0; i < ehdr->e_shnum; i++) {
glue(bswap_shdr, SZ)(shdr_table + i);
}
}
symtab = glue(find_section, SZ)(shdr_table, ehdr->e_shnum, SHT_SYMTAB);
if (!symtab)
goto fail;
syms = load_at(fd, symtab->sh_offset, symtab->sh_size);
if (!syms)
goto fail;
nsyms = symtab->sh_size / sizeof(struct elf_sym);
/* String table */
if (symtab->sh_link >= ehdr->e_shnum) {
goto fail;
}
strtab = &shdr_table[symtab->sh_link];
str = load_at(fd, strtab->sh_offset, strtab->sh_size);
if (!str) {
goto fail;
}
i = 0;
while (i < nsyms) {
if (must_swab) {
glue(bswap_sym, SZ)(&syms[i]);
}
if (sym_cb) {
sym_cb(str + syms[i].st_name, syms[i].st_info,
syms[i].st_value, syms[i].st_size);
}
/* We are only interested in function symbols.
Throw everything else away. */
if (syms[i].st_shndx == SHN_UNDEF ||
syms[i].st_shndx >= SHN_LORESERVE ||
ELF_ST_TYPE(syms[i].st_info) != STT_FUNC) {
nsyms--;
if (i < nsyms) {
syms[i] = syms[nsyms];
}
continue;
}
if (clear_lsb) {
/* The bottom address bit marks a Thumb or MIPS16 symbol. */
syms[i].st_value &= ~(glue(glue(Elf, SZ), _Addr))1;
}
i++;
}
syms = g_realloc(syms, nsyms * sizeof(*syms));
qsort(syms, nsyms, sizeof(*syms), glue(symcmp, SZ));
for (i = 0; i < nsyms - 1; i++) {
if (syms[i].st_size == 0) {
syms[i].st_size = syms[i + 1].st_value - syms[i].st_value;
}
}
/* Commit */
s = g_malloc0(sizeof(*s));
s->lookup_symbol = glue(lookup_symbol, SZ);
glue(s->disas_symtab.elf, SZ) = syms;
s->disas_num_syms = nsyms;
s->disas_strtab = str;
s->next = syminfos;
syminfos = s;
g_free(shdr_table);
return 0;
fail:
g_free(syms);
g_free(str);
g_free(shdr_table);
return -1;
}
static int glue(elf_reloc, SZ)(struct elfhdr *ehdr, int fd, int must_swab,
uint64_t (*translate_fn)(void *, uint64_t),
void *translate_opaque, uint8_t *data,
struct elf_phdr *ph, int elf_machine)
{
struct elf_shdr *reltab, *shdr_table = NULL;
struct elf_rela *rels = NULL;
int nrels, i, ret = -1;
elf_word wordval;
void *addr;
shdr_table = load_at(fd, ehdr->e_shoff,
sizeof(struct elf_shdr) * ehdr->e_shnum);
if (!shdr_table) {
return -1;
}
if (must_swab) {
for (i = 0; i < ehdr->e_shnum; i++) {
glue(bswap_shdr, SZ)(&shdr_table[i]);
}
}
reltab = glue(find_section, SZ)(shdr_table, ehdr->e_shnum, SHT_RELA);
if (!reltab) {
goto fail;
}
rels = load_at(fd, reltab->sh_offset, reltab->sh_size);
if (!rels) {
goto fail;
}
nrels = reltab->sh_size / sizeof(struct elf_rela);
for (i = 0; i < nrels; i++) {
if (must_swab) {
glue(bswap_rela, SZ)(&rels[i]);
}
if (rels[i].r_offset < ph->p_vaddr ||
rels[i].r_offset >= ph->p_vaddr + ph->p_filesz) {
continue;
}
addr = &data[rels[i].r_offset - ph->p_vaddr];
switch (elf_machine) {
case EM_S390:
switch (rels[i].r_info) {
case R_390_RELATIVE:
wordval = *(elf_word *)addr;
if (must_swab) {
bswapSZs(&wordval);
}
wordval = translate_fn(translate_opaque, wordval);
if (must_swab) {
bswapSZs(&wordval);
}
*(elf_word *)addr = wordval;
break;
default:
fprintf(stderr, "Unsupported relocation type %i!\n",
(int)rels[i].r_info);
}
}
}
ret = 0;
fail:
g_free(rels);
g_free(shdr_table);
return ret;
}
/*
* Given 'nhdr', a pointer to a range of ELF Notes, search through them
* for a note matching type 'elf_note_type' and return a pointer to
* the matching ELF note.
*/
static struct elf_note *glue(get_elf_note_type, SZ)(struct elf_note *nhdr,
elf_word note_size,
elf_word phdr_align,
elf_word elf_note_type)
{
elf_word nhdr_size = sizeof(struct elf_note);
elf_word elf_note_entry_offset = 0;
elf_word note_type;
elf_word nhdr_namesz;
elf_word nhdr_descsz;
if (nhdr == NULL) {
return NULL;
}
note_type = nhdr->n_type;
while (note_type != elf_note_type) {
nhdr_namesz = nhdr->n_namesz;
nhdr_descsz = nhdr->n_descsz;
elf_note_entry_offset = nhdr_size +
QEMU_ALIGN_UP(nhdr_namesz, phdr_align) +
QEMU_ALIGN_UP(nhdr_descsz, phdr_align);
/*
* If the offset calculated in this iteration exceeds the
* supplied size, we are done and no matching note was found.
*/
if (elf_note_entry_offset > note_size) {
return NULL;
}
/* skip to the next ELF Note entry */
nhdr = (void *)nhdr + elf_note_entry_offset;
note_type = nhdr->n_type;
}
return nhdr;
}
static int glue(load_elf, SZ)(const char *name, int fd,
uint64_t (*elf_note_fn)(void *, void *, bool),
uint64_t (*translate_fn)(void *, uint64_t),
void *translate_opaque,
int must_swab, uint64_t *pentry,
uint64_t *lowaddr, uint64_t *highaddr,
int elf_machine, int clear_lsb, int data_swab,
AddressSpace *as, bool load_rom,
symbol_fn_t sym_cb)
{
struct elfhdr ehdr;
struct elf_phdr *phdr = NULL, *ph;
int size, i, total_size;
elf_word mem_size, file_size, data_offset;
uint64_t addr, low = (uint64_t)-1, high = 0;
GMappedFile *mapped_file = NULL;
uint8_t *data = NULL;
char label[128];
int ret = ELF_LOAD_FAILED;
if (read(fd, &ehdr, sizeof(ehdr)) != sizeof(ehdr))
goto fail;
if (must_swab) {
glue(bswap_ehdr, SZ)(&ehdr);
}
if (elf_machine <= EM_NONE) {
/* The caller didn't specify an ARCH, we can figure it out */
elf_machine = ehdr.e_machine;
}
switch (elf_machine) {
case EM_PPC64:
if (ehdr.e_machine != EM_PPC64) {
if (ehdr.e_machine != EM_PPC) {
ret = ELF_LOAD_WRONG_ARCH;
goto fail;
}
}
break;
case EM_X86_64:
if (ehdr.e_machine != EM_X86_64) {
if (ehdr.e_machine != EM_386) {
ret = ELF_LOAD_WRONG_ARCH;
goto fail;
}
}
break;
case EM_MICROBLAZE:
if (ehdr.e_machine != EM_MICROBLAZE) {
if (ehdr.e_machine != EM_MICROBLAZE_OLD) {
ret = ELF_LOAD_WRONG_ARCH;
goto fail;
}
}
break;
case EM_MOXIE:
if (ehdr.e_machine != EM_MOXIE) {
if (ehdr.e_machine != EM_MOXIE_OLD) {
ret = ELF_LOAD_WRONG_ARCH;
goto fail;
}
}
break;
case EM_MIPS:
case EM_NANOMIPS:
if ((ehdr.e_machine != EM_MIPS) &&
(ehdr.e_machine != EM_NANOMIPS)) {
ret = ELF_LOAD_WRONG_ARCH;
goto fail;
}
break;
default:
if (elf_machine != ehdr.e_machine) {
ret = ELF_LOAD_WRONG_ARCH;
goto fail;
}
}
if (pentry)
*pentry = (uint64_t)(elf_sword)ehdr.e_entry;
glue(load_symbols, SZ)(&ehdr, fd, must_swab, clear_lsb, sym_cb);
size = ehdr.e_phnum * sizeof(phdr[0]);
if (lseek(fd, ehdr.e_phoff, SEEK_SET) != ehdr.e_phoff) {
goto fail;
}
phdr = g_malloc0(size);
if (!phdr)
goto fail;
if (read(fd, phdr, size) != size)
goto fail;
if (must_swab) {
for(i = 0; i < ehdr.e_phnum; i++) {
ph = &phdr[i];
glue(bswap_phdr, SZ)(ph);
}
}
/*
* Since we want to be able to modify the mapped buffer, we set the
* 'writeble' parameter to 'true'. Modifications to the buffer are not
* written back to the file.
*/
mapped_file = g_mapped_file_new_from_fd(fd, true, NULL);
if (!mapped_file) {
goto fail;
}
total_size = 0;
for(i = 0; i < ehdr.e_phnum; i++) {
ph = &phdr[i];
if (ph->p_type == PT_LOAD) {
mem_size = ph->p_memsz; /* Size of the ROM */
file_size = ph->p_filesz; /* Size of the allocated data */
data_offset = ph->p_offset; /* Offset where the data is located */
if (file_size > 0) {
if (g_mapped_file_get_length(mapped_file) <
file_size + data_offset) {
goto fail;
}
data = (uint8_t *)g_mapped_file_get_contents(mapped_file);
data += data_offset;
}
/* The ELF spec is somewhat vague about the purpose of the
* physical address field. One common use in the embedded world
* is that physical address field specifies the load address
* and the virtual address field specifies the execution address.
* Segments are packed into ROM or flash, and the relocation
* and zero-initialization of data is done at runtime. This
* means that the memsz header represents the runtime size of the
* segment, but the filesz represents the loadtime size. If
* we try to honour the memsz value for an ELF file like this
* we will end up with overlapping segments (which the
* loader.c code will later reject).
* We support ELF files using this scheme by by checking whether
* paddr + memsz for this segment would overlap with any other
* segment. If so, then we assume it's using this scheme and
* truncate the loaded segment to the filesz size.
* If the segment considered as being memsz size doesn't overlap
* then we use memsz for the segment length, to handle ELF files
* which assume that the loader will do the zero-initialization.
*/
if (mem_size > file_size) {
/* If this segment's zero-init portion overlaps another
* segment's data or zero-init portion, then truncate this one.
* Invalid ELF files where the segments overlap even when
* only file_size bytes are loaded will be rejected by
* the ROM overlap check in loader.c, so we don't try to
* explicitly detect those here.
*/
int j;
elf_word zero_start = ph->p_paddr + file_size;
elf_word zero_end = ph->p_paddr + mem_size;
for (j = 0; j < ehdr.e_phnum; j++) {
struct elf_phdr *jph = &phdr[j];
if (i != j && jph->p_type == PT_LOAD) {
elf_word other_start = jph->p_paddr;
elf_word other_end = jph->p_paddr + jph->p_memsz;
if (!(other_start >= zero_end ||
zero_start >= other_end)) {
mem_size = file_size;
break;
}
}
}
}
if (mem_size > INT_MAX - total_size) {
ret = ELF_LOAD_TOO_BIG;
goto fail;
}
/* address_offset is hack for kernel images that are
linked at the wrong physical address. */
if (translate_fn) {
addr = translate_fn(translate_opaque, ph->p_paddr);
glue(elf_reloc, SZ)(&ehdr, fd, must_swab, translate_fn,
translate_opaque, data, ph, elf_machine);
} else {
addr = ph->p_paddr;
}
if (data_swab) {
int j;
for (j = 0; j < file_size; j += (1 << data_swab)) {
uint8_t *dp = data + j;
switch (data_swab) {
case (1):
*(uint16_t *)dp = bswap16(*(uint16_t *)dp);
break;
case (2):
*(uint32_t *)dp = bswap32(*(uint32_t *)dp);
break;
case (3):
*(uint64_t *)dp = bswap64(*(uint64_t *)dp);
break;
default:
g_assert_not_reached();
}
}
}
/* the entry pointer in the ELF header is a virtual
* address, if the text segments paddr and vaddr differ
* we need to adjust the entry */
if (pentry && !translate_fn &&
ph->p_vaddr != ph->p_paddr &&
ehdr.e_entry >= ph->p_vaddr &&
ehdr.e_entry < ph->p_vaddr + ph->p_filesz &&
ph->p_flags & PF_X) {
*pentry = ehdr.e_entry - ph->p_vaddr + ph->p_paddr;
}
/* Some ELF files really do have segments of zero size;
* just ignore them rather than trying to create empty
* ROM blobs, because the zero-length blob can falsely
* trigger the overlapping-ROM-blobs check.
*/
if (mem_size != 0) {
if (load_rom) {
snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
/*
* rom_add_elf_program() takes its own reference to
* 'mapped_file'.
*/
rom_add_elf_program(label, mapped_file, data, file_size,
mem_size, addr, as);
} else {
address_space_write(as ? as : &address_space_memory,
addr, MEMTXATTRS_UNSPECIFIED,
data, file_size);
}
}
total_size += mem_size;
if (addr < low)
low = addr;
if ((addr + mem_size) > high)
high = addr + mem_size;
data = NULL;
} else if (ph->p_type == PT_NOTE && elf_note_fn) {
struct elf_note *nhdr = NULL;
file_size = ph->p_filesz; /* Size of the range of ELF notes */
data_offset = ph->p_offset; /* Offset where the notes are located */
if (file_size > 0) {
if (g_mapped_file_get_length(mapped_file) <
file_size + data_offset) {
goto fail;
}
data = (uint8_t *)g_mapped_file_get_contents(mapped_file);
data += data_offset;
}
/*
* Search the ELF notes to find one with a type matching the
* value passed in via 'translate_opaque'
*/
nhdr = (struct elf_note *)data;
assert(translate_opaque != NULL);
nhdr = glue(get_elf_note_type, SZ)(nhdr, file_size, ph->p_align,
*(uint64_t *)translate_opaque);
if (nhdr != NULL) {
bool is64 =
sizeof(struct elf_note) == sizeof(struct elf64_note);
elf_note_fn((void *)nhdr, (void *)&ph->p_align, is64);
}
data = NULL;
}
}
if (lowaddr)
*lowaddr = (uint64_t)(elf_sword)low;
if (highaddr)
*highaddr = (uint64_t)(elf_sword)high;
ret = total_size;
fail:
g_mapped_file_unref(mapped_file);
g_free(phdr);
return ret;
}
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