https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69276
Bug ID: 69276
Summary: Address sanitizer does not handle heap overflow
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: marxin at gcc dot gnu.org
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
Target Milestone: ---
Created attachment 37341
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37341&action=edit
suggested patch
Hi.
Using master of the GCC repository, following test-case can't be spotted by
address sanitizer:
$ xclip missing-store.C
#include <new>
#include <stdlib.h>
struct vec
{
int size;
};
struct vnull
{
operator vec() { return vec(); }
};
vnull vNULL;
struct A
{
A(): value2 (vNULL) {}
int value;
vec value2;
};
int main()
{
int *array = (int *)malloc (sizeof (int) * 1);
A *a = new (array) A ();
free (array);
}
$ g++ -fsanitize=address missing-store.C
$ ./a.out && echo $?
0
However, valgrind can detect that:
$ g++ missing-store.C
$ valgrind ./a.out
==11323== Memcheck, a memory error detector
==11323== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==11323== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==11323== Command: ./a.out
==11323==
==11323== Invalid write of size 4
==11323== at 0x4006EF: A::A() (in
/home/marxin/Programming/testcases/asan-clobber/a.out)
==11323== by 0x40068D: main (in
/home/marxin/Programming/testcases/asan-clobber/a.out)
==11323== Address 0x5a83c84 is 0 bytes after a block of size 4 alloc'd
==11323== at 0x4C2A00F: malloc (in
/usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==11323== by 0x400668: main (in
/home/marxin/Programming/testcases/asan-clobber/a.out)
Problem is that in asan.c we do not instrument stores that come from
gimple_call statements.
Using suggested (and untested) patch in attachment, the compiler can detect the
problem:
./a.out
=================================================================
==19667==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x60200000eff4 at pc 0x000000400a40 bp 0x7fffffffdd00 sp 0x7fffffffdcf8
WRITE of size 4 at 0x60200000eff4 thread T0
#0 0x400a3f in A::A()
/home/marxin/Programming/testcases/asan-clobber/missing-store.C:17
#1 0x40097d in main
/home/marxin/Programming/testcases/asan-clobber/missing-store.C:25
#2 0x7ffff621c60f in __libc_start_main (/lib64/libc.so.6+0x2060f)
#3 0x400878 in _start
(/home/marxin/Programming/testcases/asan-clobber/a.out+0x400878)
0x60200000eff4 is located 0 bytes to the right of 4-byte region
[0x60200000eff0,0x60200000eff4)
allocated by thread T0 here:
#0 0x7ffff6f01c28 in __interceptor_malloc
../../../../libsanitizer/asan/asan_malloc_linux.cc:38
#1 0x400958 in main
/home/marxin/Programming/testcases/asan-clobber/missing-store.C:24
#2 0x7ffff621c60f in __libc_start_main (/lib64/libc.so.6+0x2060f)
SUMMARY: AddressSanitizer: heap-buffer-overflow
/home/marxin/Programming/testcases/asan-clobber/missing-store.C:17 in A::A()
Shadow bytes around the buggy address:
0x0c047fff9da0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9db0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9dc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9dd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9de0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c047fff9df0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa[04]fa
0x0c047fff9e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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
Heap right redzone: fb
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
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
==19667==ABORTING
Can please some from sanitizer folk provide a comment about suggested approach?
Thanks,
Martin
