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PR30326, uninitialised value in objdump compare_relocs

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This is a fuzzing PR, with a testcase involving a SHF_ALLOC and
SHF_COMPRESSED SHT_RELA section, ie. a compressed dynamic reloc
section.  BFD doesn't handle compressed relocation sections, with most
of the code reading relocs using sh_size (often no bfd section is
created) but in the case of SHF_ALLOC dynamic relocs we had some code
using the bfd section size.  This led to a mismatch, sh_size is
compressed, size is uncompressed, and from that some uninitialised
memory.  Consistently using sh_size is enough to fix this PR, but I've
also added tests to exclude SHF_COMPRESSED reloc sections from
consideration.

	PR 30362
	* elf.c (bfd_section_from_shdr): Exclude reloc sections with
	SHF_COMPRESSED flag from normal reloc processing.
	(_bfd_elf_get_dynamic_reloc_upper_bound): Similarly exclude
	SHF_COMPRESSED sections from consideration.  Use sh_size when
	sizing to match slurp_relocs.
	(_bfd_elf_canonicalize_dynamic_reloc): Likewise.
	(_bfd_elf_get_synthetic_symtab): Use NUM_SHDR_ENTRIES to size
	plt relocs.
	* elf32-arm.c (elf32_arm_get_synthetic_symtab): Likewise.
	* elf32-ppc.c (ppc_elf_get_synthetic_symtab): Likewise.
	* elf64-ppc.c (ppc64_elf_get_synthetic_symtab): Likewise.
	* elfxx-mips.c (_bfd_mips_elf_get_synthetic_symtab): Likewise.
This commit is contained in:
Alan Modra 2023-04-12 11:00:42 +09:30
parent 32011d23a8
commit 93c6e8c3c1
5 changed files with 14 additions and 11 deletions
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17
bfd/elf.c
View File

@ -2381,6 +2381,7 @@ bfd_section_from_shdr (bfd *abfd, unsigned int shindex)
its sh_link points to the null section. */
if (((abfd->flags & (DYNAMIC | EXEC_P)) != 0
&& (hdr->sh_flags & SHF_ALLOC) != 0)
|| (hdr->sh_flags & SHF_COMPRESSED) != 0
|| hdr->sh_type == SHT_RELR
|| hdr->sh_link == SHN_UNDEF
|| hdr->sh_link != elf_onesymtab (abfd)
@ -8728,15 +8729,16 @@ _bfd_elf_get_dynamic_reloc_upper_bound (bfd *abfd)
for (s = abfd->sections; s != NULL; s = s->next)
if (elf_section_data (s)->this_hdr.sh_link == elf_dynsymtab (abfd)
&& (elf_section_data (s)->this_hdr.sh_type == SHT_REL
|| elf_section_data (s)->this_hdr.sh_type == SHT_RELA))
|| elf_section_data (s)->this_hdr.sh_type == SHT_RELA)
&& (elf_section_data (s)->this_hdr.sh_flags & SHF_COMPRESSED) == 0)
{
ext_rel_size += s->size;
if (ext_rel_size < s->size)
ext_rel_size += elf_section_data (s)->this_hdr.sh_size;
if (ext_rel_size < elf_section_data (s)->this_hdr.sh_size)
{
bfd_set_error (bfd_error_file_truncated);
return -1;
}
count += s->size / elf_section_data (s)->this_hdr.sh_entsize;
count += NUM_SHDR_ENTRIES (&elf_section_data (s)->this_hdr);
if (count > LONG_MAX / sizeof (arelent *))
{
bfd_set_error (bfd_error_file_too_big);
@ -8785,14 +8787,15 @@ _bfd_elf_canonicalize_dynamic_reloc (bfd *abfd,
{
if (elf_section_data (s)->this_hdr.sh_link == elf_dynsymtab (abfd)
&& (elf_section_data (s)->this_hdr.sh_type == SHT_REL
|| elf_section_data (s)->this_hdr.sh_type == SHT_RELA))
|| elf_section_data (s)->this_hdr.sh_type == SHT_RELA)
&& (elf_section_data (s)->this_hdr.sh_flags & SHF_COMPRESSED) == 0)
{
arelent *p;
long count, i;
if (! (*slurp_relocs) (abfd, s, syms, true))
return -1;
count = s->size / elf_section_data (s)->this_hdr.sh_entsize;
count = NUM_SHDR_ENTRIES (&elf_section_data (s)->this_hdr);
p = s->relocation;
for (i = 0; i < count; i++)
*storage++ = p++;
@ -12936,7 +12939,7 @@ _bfd_elf_get_synthetic_symtab (bfd *abfd,
if (! (*slurp_relocs) (abfd, relplt, dynsyms, true))
return -1;
count = relplt->size / hdr->sh_entsize;
count = NUM_SHDR_ENTRIES (hdr);
size = count * sizeof (asymbol);
p = relplt->relocation;
for (i = 0; i < count; i++, p += bed->s->int_rels_per_ext_rel)

2
bfd/elf32-arm.c
View File

@ -20067,7 +20067,7 @@ elf32_arm_get_synthetic_symtab (bfd *abfd,
plt->flags |= SEC_IN_MEMORY;
}
count = relplt->size / hdr->sh_entsize;
count = NUM_SHDR_ENTRIES (hdr);
size = count * sizeof (asymbol);
p = relplt->relocation;
for (i = 0; i < count; i++, p += elf32_arm_size_info.int_rels_per_ext_rel)

2
bfd/elf32-ppc.c
View File

@ -1920,7 +1920,7 @@ ppc_elf_get_synthetic_symtab (bfd *abfd, long symcount, asymbol **syms,
}
}
count = relplt->size / sizeof (Elf32_External_Rela);
count = NUM_SHDR_ENTRIES (&elf_section_data (relplt)->this_hdr);
/* If the stubs are those for -shared/-pie then we might have
multiple stubs for each plt entry. If that is the case then
there is no way to associate stubs with their plt entries short

2
bfd/elf64-ppc.c
View File

@ -2576,7 +2576,7 @@ ppc64_elf_get_synthetic_symtab (bfd *abfd,
if (!(*slurp_relocs) (abfd, relplt, dyn_syms, true))
goto free_contents_and_exit_err;
plt_count = relplt->size / sizeof (Elf64_External_Rela);
plt_count = NUM_SHDR_ENTRIES (&elf_section_data (relplt)->this_hdr);
size += plt_count * sizeof (asymbol);
p = relplt->relocation;

2
bfd/elfxx-mips.c
View File

@ -16595,7 +16595,7 @@ _bfd_mips_elf_get_synthetic_symtab (bfd *abfd,
/* Calculating the exact amount of space required for symbols would
require two passes over the PLT, so just pessimise assuming two
PLT slots per relocation. */
count = relplt->size / hdr->sh_entsize;
count = NUM_SHDR_ENTRIES (hdr);
counti = count * bed->s->int_rels_per_ext_rel;
size = 2 * count * sizeof (asymbol);
size += count * (sizeof (mipssuffix) +