[Bug sanitizer/108085] gcc trunk's ASAN at -O3 missed a stack-use-after-scope

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108085

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|                            |2022-12-14
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1

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

Note I can't reproduce it with Clang with any of -O1+ options:

$ clang pr108085.c -fsanitize=address -w && ./a.out
=================================================================
==20150==ERROR: AddressSanitizer: stack-use-after-scope on address
0x7ffff5e00030 at pc 0x55555566a2aa bp 0x7fffffffd510 sp 0x7fffffffd508
READ of size 4 at 0x7ffff5e00030 thread T0
    #0 0x55555566a2a9 in main pr108085.c
    #1 0x7ffff7ca35af in __libc_start_call_main (/lib64/libc.so.6+0x275af)
(BuildId: 3f7f40d4302fa8a9568a057065c023bf137fceb7)
    #2 0x7ffff7ca3678 in __libc_start_main@GLIBC_2.2.5
(/lib64/libc.so.6+0x27678) (BuildId: 3f7f40d4302fa8a9568a057065c023bf137fceb7)
    #3 0x5555555a9d64 in _start
/home/abuild/rpmbuild/BUILD/glibc-2.36/csu/../sysdeps/x86_64/start.S:115

Address 0x7ffff5e00030 is located in stack of thread T0 at offset 48 in frame
    #0 0x55555566a11f in main pr108085.c

  This frame has 2 object(s):
    [32, 36) 'd'
    [48, 52) 'f' <== Memory access at offset 48 is inside 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-use-after-scope pr108085.c in main
Shadow bytes around the buggy address:
  0x10007ebb7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007ebb7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007ebb7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007ebb7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007ebb7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10007ebb8000: f1 f1 f1 f1 04 f2[f8]f3 00 00 00 00 00 00 00 00
  0x10007ebb8010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007ebb8020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007ebb8030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007ebb8040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007ebb8050: 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
==20150==ABORTING

$ clang pr108085.c -fsanitize=address -w -O1 && ./a.out
(no output)