[Bug other/86198] New: Libbacktrace does not properly work with ".note.gnu.build-id" section

[d.khalikov at partner dot samsung.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86198

            Bug ID: 86198
           Summary: Libbacktrace does not properly work with
                    ".note.gnu.build-id" section
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: d.khalikov at partner dot samsung.com
  Target Milestone: ---

An error happens when libbacktrace is reading ".note.gnu.build-id" section and
effects the feature which allows to read stripped debuginfo with build-id.

Steps to reproduce:
(I will use libasan in my test case, because it's easy and libbacktrace is a
default symbolizer for libasan in GCC).

1.$cat a.cc
int main () {
  int *ptr = new int[1];
  return ptr[1];
}

2.$g++ -o a a.cc -fsanitize=address -g 
-Wl,--build-id=0x0123456789abcdef0123456789abcdef01234567

3.$objcopy --only-keep-debug a a.debug

4.$strip a

5. In this step we need a superuser rights:
#mkdir /usr/lib/debug/.build-id/01
#ln -s  `pwd`/a.debug
/usr/lib/debug/.build-id/01/23456789abcdef0123456789abcdef01234567.debug

6. ./a

output:
...
#0 0x4007cf  (/path/to/exe/a+0x4007cf)
...

The problem at the libbacktrace/elf.c line 2871

2866           buildid_view_valid = 1;
2867           note = (const b_elf_note *) buildid_view.data;
2868           if (note->type == NT_GNU_BUILD_ID
2869               && note->namesz == 4
2870               && strncmp (note->name, "GNU", 4) == 0
2871               && shdr->sh_size < 12 + ((note->namesz + 3) & ~ 3) +
note->descsz)
2872             {
2873               buildid_data = &note->name[0] + ((note->namesz + 3) & ~ 3);
2874               buildid_size = note->descsz;
2875             }
2876         }

The size for the ".note.gnu.build-id" section by default is 36 bytes (12 + 4 +
20)
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/developer_guide/compiling-build-id

So, the cmp on line 2871 should be changed from less to less or equal

2871               && shdr->sh_size <= 12 + ((note->namesz + 3) & ~ 3) +
note->descsz)