[Bug sanitizer/108904] New: ASAN at -O2/3 missed a global buffer overflow

[Bug sanitizer/108904] New: ASAN at -O2/3 missed a global buffer overflow

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108904

            Bug ID: 108904
           Summary: ASAN at -O2/3 missed 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, ASAN at -O2/3 missed the global-buffer-overflow.

Compiler explorer: https://godbolt.org/z/zjed8vzhj

% cat a.c
int a, b, c = 3, d;
static int *e = &c, *f, *g = &e;
short h, i;
int(j)(int k) { 
    return k==0 ?0: a; 
}
int *l(int* p) { return &b; }
int main() {
  for (; h >= 0; h--) {
    b = j(*e);
    if (*e | *(&d + 1))
      ++i;
  }
  f = l(g);
  __builtin_printf("%d\n", i);
}
%
% gcc-tk -O2 -fsanitize=address -w a.c && ./a.out
1
% gcc-tk -O1 -fsanitize=address -w a.c && ./a.out
=================================================================
==1==ERROR: AddressSanitizer: global-buffer-overflow on address 0x000000404424
at pc 0x0000004011fd bp 0x7ffe0ae032c0 sp 0x7ffe0ae032b8
READ of size 4 at 0x000000404424 thread T0
    #0 0x4011fc in main /app/a.c:11
    #1 0x7fb7968aa082 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId:
1878e6b475720c7c51969e69ab2d276fae6d1dee)
    #2 0x4010bd in _start (/app/a.s+0x4010bd) (BuildId:
ad1fc5fb90a08d043b6c529370650d444b96c26e)

0x000000404424 is located 60 bytes before global variable 'b' defined in
'/app/a.c' (0x404460) of size 4
0x000000404424 is located 0 bytes after global variable 'd' defined in
'/app/a.c' (0x404420) of size 4
...
%

[Bug sanitizer/108904] ASAN at -O2/3 missed a global buffer overflow

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108904

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

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

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
>     if (*e | *(&d + 1))

*e is always true, thus it's optimized out.