[Bug sanitizer/105405] New: missed buffer-overflow in -O0

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105405

            Bug ID: 105405
           Summary: missed buffer-overflow in -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` would miss the report,
while `gcc -fsanitize=address -O3` would not.

$cat a.c
main() {
  int a[1][1];
  {
    int *b[1];
  }
  a[1][3]++;
}
$
$gcc -fsanitize=address -w -O0 a.c ; ./a.out
$
$gcc -fsanitize=address -w -O3 a.c ; ./a.out
=================================================================
==6342==ERROR: AddressSanitizer: stack-buffer-overflow on address
0x7f8843a00030 at pc 0x0000004010f9 bp 0x7fff0b7f6a40 sp 0x7fff0b7f6a38
READ of size 4 at 0x7f8843a00030 thread T0
    #0 0x4010f8 in main
(/shared/mutate/array/trial_new/work0/debug40/a.out+0x4010f8)
    #1 0x7f8845c570b2 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x240b2)
    #2 0x40117d in _start
(/shared/mutate/array/trial_new/work0/debug40/a.out+0x40117d)

Address 0x7f8843a00030 is located in stack of thread T0 at offset 48 in frame
    #0 0x40107f in main
(/shared/mutate/array/trial_new/work0/debug40/a.out+0x40107f)

  This frame has 1 object(s):
    [32, 36) 'a' (line 2) <== Memory access at offset 48 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
(/shared/mutate/array/trial_new/work0/debug40/a.out+0x4010f8) in main
Shadow bytes around the buggy address:
  0x0ff188737fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff188737fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff188737fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff188737fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff188737ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0ff188738000: f1 f1 f1 f1 04 f3[f3]f3 00 00 00 00 00 00 00 00
  0x0ff188738010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff188738020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff188738030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff188738040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff188738050: 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
==6342==ABORTING