From b3601167d7a4c9f34eb65c3892c9ef25e3c1c66f Mon Sep 17 00:00:00 2001 From: Andrei Homescu Date: Mon, 28 Jun 2021 18:26:53 -0700 Subject: [PATCH] libelf: Fix unaligned d_off offsets for input sections with large alignments The mkl_memory_patched.o object inside the libmkl_core.a library from the Intel Math Kernel Library version 2018.2.199 has this section with an alignment of 4096 and offset of 0xb68: [ 2] .data PROGBITS 0000000000000000 000b68 011000 00 WA 0 0 4096 Reading this file with libelf and trying to write it back to disk triggers the following sequence of events: 1) code in elf_getdata.c clamps d_align for this section's data buffer to the section's offset 2) code in elf32_updatenull.c checks if the alignment is a power of two and incorrectly returns an error This commit fixes this corner case by increasing the alignment to the next power of two after the clamping, so the check passes. A test that reproduces this bug using strip is also included. Signed-off-by: Andrei Homescu --- libelf/ChangeLog | 5 +++++ libelf/elf_getdata.c | 13 +++++++++++- tests/ChangeLog | 12 +++++++++-- tests/Makefile.am | 5 +++-- tests/run-strip-largealign.sh | 35 ++++++++++++++++++++++++++++++++ tests/testfile-largealign.o.bz2 | Bin 0 -> 183 bytes 6 files changed, 65 insertions(+), 5 deletions(-) create mode 100755 tests/run-strip-largealign.sh create mode 100644 tests/testfile-largealign.o.bz2 diff --git a/libelf/ChangeLog b/libelf/ChangeLog index a1fd414c3..62437c557 100644 --- a/libelf/ChangeLog +++ b/libelf/ChangeLog @@ -1,3 +1,8 @@ +2021-06-09 Andrei Homescu + + * elf_getdata.c: Fix d_align for sections where alignment is larger + than offset. + 2020-12-12 Mark Wielaard * elf.h: Update from glibc. diff --git a/libelf/elf_getdata.c b/libelf/elf_getdata.c index 6ed44504f..3cad29de5 100644 --- a/libelf/elf_getdata.c +++ b/libelf/elf_getdata.c @@ -384,7 +384,18 @@ __libelf_set_rawdata_wrlock (Elf_Scn *scn) which should be uncommon. */ align = align ?: 1; if (type != SHT_NOBITS && align > offset) - align = offset; + { + /* Align the offset to the next power of two. Uses algorithm from + https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2 */ + align = offset - 1; + align |= align >> 1; + align |= align >> 2; + align |= align >> 4; + align |= align >> 8; + align |= align >> 16; + align |= align >> 32; + align++; + } scn->rawdata.d.d_align = align; if (elf->class == ELFCLASS32 || (offsetof (struct Elf, state.elf32.ehdr) diff --git a/tests/ChangeLog b/tests/ChangeLog index b65cbeb7d..28aaf85e6 100644 --- a/tests/ChangeLog +++ b/tests/ChangeLog @@ -1,7 +1,15 @@ +2021-06-09 Andrei Homescu + + * testfile-largealign.o.bz2: New test file. + * run-strip-largealign.sh: New test. + * Makefile.am (TESTS): Add run-strip-largealign.sh. + (EXTRA_DIST): Add run-strip-largealign.sh and + testfile-largealign.o.bz2 + 2021-07-02 Mark Wielaard - * run-debuginfo-find.sh: unset VALGRIND_CMD before testing debuginfod - client cache. + * run-debuginfo-find.sh: unset VALGRIND_CMD before testing debuginfod + client cache. 2021-06-16 Frank Ch. Eigler diff --git a/tests/Makefile.am b/tests/Makefile.am index 762042771..8ac0d2e6d 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -189,7 +189,7 @@ TESTS = run-arextract.sh run-arsymtest.sh run-ar.sh newfile test-nlist \ leb128 read_unaligned \ msg_tst system-elf-libelf-test \ $(asm_TESTS) run-disasm-bpf.sh run-low_high_pc-dw-form-indirect.sh \ - run-readelf-dw-form-indirect.sh + run-readelf-dw-form-indirect.sh run-strip-largealign.sh if !BIARCH export ELFUTILS_DISABLE_BIARCH = 1 @@ -511,7 +511,8 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh run-ar.sh \ testfile_pt_gnu_prop.bz2 testfile_pt_gnu_prop32.bz2 \ run-getphdrnum.sh testfile-phdrs.elf.bz2 \ run-test-includes.sh run-low_high_pc-dw-form-indirect.sh \ - run-readelf-dw-form-indirect.sh testfile-dw-form-indirect.bz2 + run-readelf-dw-form-indirect.sh testfile-dw-form-indirect.bz2 \ + testfile-largealign.bz2 run-strip-largealign.sh if USE_VALGRIND diff --git a/tests/run-strip-largealign.sh b/tests/run-strip-largealign.sh new file mode 100755 index 000000000..4f81d3c18 --- /dev/null +++ b/tests/run-strip-largealign.sh @@ -0,0 +1,35 @@ +#! /bin/sh +# Copyright (C) 2021 Runsafe Security, Inc. +# This file is part of elfutils. +# +# This file is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# elfutils is distributed in the hope that it will be useful, but +# WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . +# + +. $srcdir/test-subr.sh + +# = testfile-largealign.S = +# section .data +# align 4096 +# dd 0x12345678 +# +# nasm -f elf64 -o testfile-largealign.o testfile-largealign.S + +infile=testfile-largealign.o +outfile=$infile.stripped + +testfiles $infile +tempfiles $outfile + +testrun ${abs_top_builddir}/src/strip -o $outfile $infile +testrun ${abs_top_builddir}/src/elflint --gnu $outfile diff --git a/tests/testfile-largealign.o.bz2 b/tests/testfile-largealign.o.bz2 new file mode 100644 index 0000000000000000000000000000000000000000..324c1eae376dab373d4860188d1c29d577b64abc GIT binary patch literal 183 zc-jHC07(BrT4*^jL0KkKS$lTN?*IUO|K$Gs@n9qY1_MJx2>>=i9ALlzKmb4hAON5M zfHcu5lL%>%qalz6gBn8_42FY2qd*z}8W~!#9HOGvK}7V;m`k9kmnQ7Xs*(clq9*|2 zA}D|*im9-mNr*r@N){aWV)s@c9Zj;%)REkP6oAtzQc;Q^velES!XQ@Wspq}yD~@;F lCD&sZA1p^UFHqN<4rm_o_X>?mK--t`cO+AV2?w`qzVN>OO*jAm literal 0 Hc-jL100001 -- 2.47.2