https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108637
Bug ID: 108637
Summary: ASAN at -O2 misses a stack-use-after-scope
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 cannot detect the stack-use-after-scope.
This happens since GCC-11. GCC-10 and below work fine.
I understand that there is a type-incompatible warning. But I believe it should
not affect the ASAN anyway.
Compiler explorer: https://godbolt.org/z/WcbadP961
% cat a.c
char a, b, c;
short d;
int main() {
{
long e = a;
for (; b <= 0; b++) {
char *f;
d = 2;
for (; d; d--) {
int g = 111;
f = &g;
if (e)
c = 0;
}
*f += 1;
a = *f;
}
}
}
%
% gcc-tk -fsanitize=address -O2 a.c && ./a.out
%
% gcc-tk -fsanitize=address -O1 a.c && ./a.out
=================================================================
==1==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7fb285e00020
at pc 0x000000401272 bp 0x7ffda17739c0 sp 0x7ffda17739b8
READ of size 1 at 0x7fb285e00020 thread T0
#0 0x401271 in main /a.c:15
#1 0x7fb28883d082 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId:
1878e6b475720c7c51969e69ab2d276fae6d1dee)
#2 0x4010bd in _start (/output.s+0x4010bd) (BuildId:
cb6e8e9c15b7d8e5515d7e6b8591d2b77b5f3e21)
Address 0x7fb285e00020 is located in stack of thread T0 at offset 32 in frame
#0 0x401185 in main /a.c:3
This frame has 1 object(s):
[32, 36) 'g' (line 10) <== Memory access at offset 32 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 /a.c:15 in main
Shadow bytes around the buggy address:
...
%
