https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105107
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> --- There's expanded version of the testcase: $ cat pr105107.c int h=1; int *a=&h; int **b = &a; int e; void fn1() { int e=0; int **f = &a; __builtin_printf ("addr of e=%p\n", &e); *f = &e; } void i() { int g[9]; __builtin_printf ("write to %p\n", *b); **b = 5; } int main() { fn1(); i(); return 0; } $ gcc-11 pr105107.c -fsanitize=address -g && ./a.out addr of e=0x7fffffffdaf0 write to 0x7fffffffdaf0 ================================================================= ==6753==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fffffffdaf0 at pc 0x000000401416 bp 0x7fffffffda80 sp 0x7fffffffda78 WRITE of size 4 at 0x7fffffffdaf0 thread T0 #0 0x401415 in i /home/marxin/Programming/testcases/pr105107.c:19 #1 0x401493 in main /home/marxin/Programming/testcases/pr105107.c:25 #2 0x7ffff73be62f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58 #3 0x7ffff73be6ef in __libc_start_main_impl ../csu/libc-start.c:392 #4 0x4010f4 in _start (/home/marxin/Programming/testcases/a.out+0x4010f4) Address 0x7fffffffdaf0 is located in stack of thread T0 at offset 96 in frame #0 0x401305 in i /home/marxin/Programming/testcases/pr105107.c:16 This frame has 1 object(s): [48, 84) 'g' (line 17) <== Memory access at offset 96 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 /home/marxin/Programming/testcases/pr105107.c:19 in i Shadow bytes around the buggy address: 0x10007fff7b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7b10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7b20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7b30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7b40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>0x10007fff7b50: 00 00 f1 f1 f1 f1 f1 f1 00 00 00 00 04 f3[f3]f3 0x10007fff7b60: f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7b70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7b90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7ba0: 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 Shadow gap: cc ==6753==ABORTING The error is correct as it takes the address of 'e' in function 'fn1' where it writes once fn1 returns.