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[ELF.h] - Check the case when e_shstrndx=SHN_XINDEX, but the corresponding sh_link is broken.
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Authored by grimar on Jul 29 2019, 3:10 AM.

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Reviewers

jhenderson
MaskRay
alexander-shaposhnikov

Commits

rGa74aa23065cc: [ELF.h] - Check the case when e_shstrndx=SHN_XINDEX, but the corresponding…
rL368139: [ELF.h] - Check the case when e_shstrndx=SHN_XINDEX, but the corresponding…

Summary

When e_shstrndx is equal to SHN_XINDEX,
the index of the section string table section should
be taken from the sh_link field of the section
header at index 0.

If sh_link is broken, e.g. contains an index that is
larger than number of sections, then error is reported.

This error message was untested before.

This is almost the same as D65388, but now the code
in ELF.h is tested.

Diff Detail

Event Timeline

grimar created this revision.Jul 29 2019, 3:10 AM

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jhenderson mentioned this in D65388: [llvm-readelf/llvm-readobj] - Test the case when e_shstrndx==SHN_XINDEX, but sec[0].sh_link is broken..Jul 30 2019, 6:15 AM

should be taken from zero section sh_link field

the sh_link field of the section header at index 0?

test/Object/invalid.test
610	null section -> the section header at index 0

This revision is now accepted and ready to land.Jul 31 2019, 5:03 AM

Addressed comments.

James, since this is independent from D65388,
are you OK to land it?

Ping. James?

LGTM, with nits fixed. Sorry, last week was very busy. Just working through my backlog now.

test/Object/invalid.test
611	contains the index of a larger than the number

In D65391#1616494, @jhenderson wrote:

LGTM, with nits fixed. Sorry, last week was very busy. Just working through my backlog now.

No worries, thanks for review!

Closed by commit rL368139: [ELF.h] - Check the case when e_shstrndx=SHN_XINDEX, but the corresponding… (authored by grimar). · Explain WhyAug 7 2019, 2:28 AM

This revision was automatically updated to reflect the committed changes.

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Revision Contents

Path

Size

include/

llvm/

Object/

ELF.h

1 line

test/

Object/

invalid.test

20 lines

Diff 212143

include/llvm/Object/ELF.h

	Show First 20 Lines • Show All 460 Lines • ▼ Show 20 Lines
	Expected<StringRef>			Expected<StringRef>
	ELFFile<ELFT>::getSectionStringTable(Elf_Shdr_Range Sections) const {			ELFFile<ELFT>::getSectionStringTable(Elf_Shdr_Range Sections) const {
	uint32_t Index = getHeader()->e_shstrndx;			uint32_t Index = getHeader()->e_shstrndx;
	if (Index == ELF::SHN_XINDEX)			if (Index == ELF::SHN_XINDEX)
	Index = Sections[0].sh_link;			Index = Sections[0].sh_link;

	if (!Index) // no section string table.			if (!Index) // no section string table.
	return "";			return "";
	// TODO: Test a case when the sh_link of the section with index 0 is broken.
	if (Index >= Sections.size())			if (Index >= Sections.size())
	return createError("section header string table index " + Twine(Index) +			return createError("section header string table index " + Twine(Index) +
	" does not exist");			" does not exist");
	return getStringTable(&Sections[Index]);			return getStringTable(&Sections[Index]);
	}			}

	template <class ELFT> ELFFile<ELFT>::ELFFile(StringRef Object) : Buf(Object) {}			template <class ELFT> ELFFile<ELFT>::ELFFile(StringRef Object) : Buf(Object) {}

	▲ Show 20 Lines • Show All 239 Lines • Show Last 20 Lines

test/Object/invalid.test

	Show First 20 Lines • Show All 600 Lines • ▼ Show 20 Lines

	--- !ELF			--- !ELF
	FileHeader:			FileHeader:
	Class: ELFCLASS64			Class: ELFCLASS64
	Data: ELFDATA2LSB			Data: ELFDATA2LSB
	Type: ET_REL			Type: ET_REL
	Machine: EM_X86_64			Machine: EM_X86_64
	SHOffset: 0xffffffffffffffff			SHOffset: 0xffffffffffffffff

				## Check the case when e_shstrndx == SHN_XINDEX, but null section's sh_link contains
				MaskRayUnsubmitted Done Reply Inline Actions null section -> the section header at index 0 MaskRay: null section -> the section header at index 0
				## index of section header string table that is larger than number of the sections.
				jhendersonUnsubmitted Not Done Reply Inline Actions contains the index of a larger than the number jhenderson: contains the index of a larger than the number

				# RUN: yaml2obj --docnum=29 %s -o %t29
				# RUN: not llvm-objcopy %t29 2>&1 \| FileCheck %s -DFILE=%t29 --check-prefix=INVALID-SHSTRTAB-INDEX

				# INVALID-SHSTRTAB-INDEX: error: section header string table index 255 does not exist

				--- !ELF
				FileHeader:
				Class: ELFCLASS64
				Data: ELFDATA2LSB
				Type: ET_REL
				Machine: EM_X86_64
				## SHN_XINDEX == 0xffff.
				SHStrNdx: 0xffff
				Sections:
				- Type: SHT_NULL
				Link: 0xff