[Bug sanitizer/107747] New: gcc trunk at -Os misses a global-buffer-overflow

[Bug sanitizer/107747] New: gcc trunk at -Os misses a global-buffer-overflow

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107747

            Bug ID: 107747
           Summary: gcc trunk at -Os misses a global-buffer-overflow
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaohua.li at inf dot ethz.ch
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at gcc dot gnu.org
  Target Milestone: ---

For the following code, `gcc-trunk -Os -fsanitize=address` misses the
global-buffer-overflow, while `gcc-trunk -Ox -fsanitize=address` (x=0,1, 2, 3)
can detect it.

gcc-12 can detect the global-buffer-overflow at all optimization levels.
clang-tk can also detect it at all optimization levels.

Compiler explorer: https://godbolt.org/z/j6vh4hhaq

% cat a.c
int a, e = 2;
long b;
int *c = &a;
char *d;
void main() {
  *c = 0;
  c = c + 1;
  if (*c = e || (*d = 0))
    for (; b;)
      ;
}
%
% gcc-tk -Os -fsanitize=address a.c && ./a.out
%
% gcc-tk -O3 -fsanitize=address a.c && ./a.out
=================================================================
==1==ERROR: AddressSanitizer: global-buffer-overflow on address 0x000000404344
at pc 0x000000401159 bp 0x7fff230c86c0 sp 0x7fff230c86b8
WRITE of size 4 at 0x000000404344 thread T0
    #0 0x401158 in main /app/example.c:8
    #1 0x7fe78f129082 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId:
1878e6b475720c7c51969e69ab2d276fae6d1dee)
    #2 0x4011cd in _start (/app/output.s+0x4011cd) (BuildId:
864a1d27e04c540136a2c693324ee073ba4b3fa0)

0x000000404344 is located 0 bytes after global variable 'a' defined in
'/app/example.c' (0x404340) of size 4
SUMMARY: AddressSanitizer: global-buffer-overflow /app/example.c:8 in main
Shadow bytes around the buggy address:
  0x000000404080: 00 f9 f9 f9 f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9
  0x000000404100: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9
  0x000000404180: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x000000404200: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x000000404280: f9 f9 f9 f9 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9
=>0x000000404300: 00 f9 f9 f9 f9 f9 f9 f9[04]f9 f9 f9 f9 f9 f9 f9
  0x000000404380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000000404400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000000404480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000000404500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000000404580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==1==ABORTING
%

[Bug sanitizer/107747] gcc trunk at -Os misses a global-buffer-overflow

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107747

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |marxin at gcc dot gnu.org
   Last reconfirmed|                            |2022-11-21
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
I will take a look.

[Bug sanitizer/107747] gcc trunk at -Os misses a global-buffer-overflow

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107747

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|ASSIGNED                    |RESOLVED

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
Can't reproduce, also GCC master reports the issue.