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From: "mark at klomp dot org" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug libdw/28720] UBSan: member access within misaligned address
 0x7f6e8d80f142 for type 'struct Elf32_Phdr', which requires 4 byte alignment
Date: Tue, 04 Jan 2022 21:37:53 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28720

--- Comment #10 from Mark Wielaard <mark at klomp dot org> ---
(In reply to Evgeny Vereshchagin from comment #8)
> (In reply to Mark Wielaard from comment #7)
> > commit 9f70a762ab88ceebb8a48a7c9c3ce39ff7f205af
> > Author: Mark Wielaard <mark@klomp.org>
> > Date:   Fri Dec 24 02:01:32 2021 +0100
> >=20
> >     libdwfl: Calculate addr to read by hand in link_map.c read_addrs.
> >=20=20=20=20=20
> >     The gcc undefined sanitizer doesn't like the trick we use to calcul=
ate
> >     the (possibly) unaligned addresses to read. So calculate them by ha=
nd
> >     as unsigned char pointers.
> >=20=20=20=20=20
> >     https://sourceware.org/bugzilla/show_bug.cgi?id=3D28720
> >=20=20=20=20=20
> >     Signed-off-by: Mark Wielaard <mark@klomp.org>
> >=20
> > Which should this particular issue.
>=20
>=20
> I'm not sure but it seems it can still be triggered with that commit appl=
ied:
> ```
> $ git log --oneline -5
> 9f70a762 (HEAD -> master, origin/master, origin/HEAD) libdwfl: Calculate
> addr to read by hand in link_map.c read_addrs.
> 5b490793 libdwfl: Call xlatetom on aligned buffers in dwfl_link_map_report
> 1cf73965 libdwfl: Make sure dwfl_elf_phdr_memory_callback returns at least
> minread
> 4fdd8588 libdwfl: Always clean up build_id.memory
> 8f8c78cc libdwfl: Handle unaligned Nhdr in dwfl_segment_report_module
>=20
> $ autoreconf -i -f
> $ ./configure --enable-maintainer-mode --enable-sanitize-undefined
> $ make -j$(nproc) V=3D1
>=20
> $ UBSAN_OPTIONS=3Dprint_stacktrace=3D1:print_summary=3D1:halt_on_error=3D1
> LD_LIBRARY_PATH=3D"./libdw;./libelf" ./src/stack --core
> ./attachment.cgi\?id\=3D13875
> gelf_xlate.h:48:1: runtime error: member access within misaligned address
> 0x7f5cd5612077 for type 'struct Elf32_Dyn', which requires 4 byte alignme=
nt

That is a different issue than the one reported in comment #5.
This bug might be split up for the different issues found.

--=20
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