[Bug sanitizer/105396] New: missed stack-buffer-overflow by -O0

["shaohua.li at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105396

            Bug ID: 105396
           Summary: missed stack-buffer-overflow by -O0
           Product: gcc
           Version: 12.0
            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 -fsanitize=address -O0` misses the
buffer-overflow, while `gcc -fsanitize=address -O3` catches it.

$cat a.c
int main() {
  int a;
  int *b[1];
  int c[10];
  int d[1][1];
  for (a = 0; a < 1; a++)
    d[1][a] = 0;
}
$
$gcc -fsanitize=address -O0;./a.out
$
$gcc -fsanitize=address -O3;./a.out
==1==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fffda35c0d4
at pc 0x000000401104 bp 0x7fffda35c0a0 sp 0x7fffda35c098
WRITE of size 4 at 0x7fffda35c0d4 thread T0
    #0 0x401103 in main /app/example.c:8
    #1 0x7fc3351380b2 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x240b2)
    #2 0x40118d in _start (/app/output.s+0x40118d)

Address 0x7fffda35c0d4 is located in stack of thread T0 at offset 36 in frame
    #0 0x40107f in main /app/example.c:2

  This frame has 1 object(s):
    [32, 36) 'd' (line 6) <== Memory access at offset 36 overflows this
variable
HINT: this may be a false positive if your program uses some custom stack
unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow /app/example.c:8 in main
Shadow bytes around the buggy address:
  0x10007b4637c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007b4637d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007b4637e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007b4637f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007b463800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10007b463810: 00 00 00 00 00 00 f1 f1 f1 f1[04]f3 f3 f3 00 00
  0x10007b463820: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007b463830: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007b463840: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007b463850: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007b463860: 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