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* [Bug c/99168] New: inconsistent behavior on -O0 and -O2 with ASAN on
@ 2021-02-19 16:44 zhan3299 at purdue dot edu
2021-02-19 16:57 ` [Bug c/99168] " zhan3299 at purdue dot edu
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: zhan3299 at purdue dot edu @ 2021-02-19 16:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99168
Bug ID: 99168
Summary: inconsistent behavior on -O0 and -O2 with ASAN on
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: zhan3299 at purdue dot edu
Target Milestone: ---
I am not sure whether the following problem is caused by ASAN or O2.
Following code has different behaviors between "-fsanitize=address -O0" and
"-fsanitize=address -O2"
It affects my local 7.5.0, 10.2.0, and 11.0.0 on godbolt.
O0 (succ): https://godbolt.org/z/zMKP6K
O1 (succ): https://godbolt.org/z/Yf3oP7
O2 (fail): https://godbolt.org/z/erahvc
O3 (fail): https://godbolt.org/z/7zaqaf
Os (fail): https://godbolt.org/z/38e6xc
-----
$ cat test.c
#include <stdio.h>
struct my_struct {
unsigned long volatile x;
} __attribute__((aligned(128)));
static int k[5][6] = {};
static struct my_struct s1 = {0UL};
static struct my_struct s2 __attribute__((aligned(32))) = {0UL};
int main() {
int i, j;
for (i = 0; i < 5; i++) {
for (j = 0; j < 6; j++) {
printf("%d\n", k[i][j]);
}
}
printf("%lu\n", s1.x);
printf("%lu\n", s2.x);
return 0;
}
$ gcc test.c -Wall -fsanitize=address -O0 -o g0.out
# no any warning or error
$ gcc test.c -Wall -fsanitize=address -O2 -o g2.out
# no any warning or error
$ ./g0.out
... # normal output
$ ./g2.out
=================================================================
==26165==ERROR: AddressSanitizer: global-buffer-overflow on address
0x55a5cf268184 at pc 0x55a5cf267201 bp 0x7ffd23b80f60 sp 0x7ffd23b80f50
READ of size 4 at 0x55a5cf268184 thread T0
#0 0x55a5cf267200 in main
(/root/docker_share/csmith/gcc_self_10/g2.out+0x1200)
#1 0x7efea78c10b2 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
#2 0x55a5cf26726d in _start
(/root/docker_share/csmith/gcc_self_10/g2.out+0x126d)
0x55a5cf268184 is located 4 bytes inside of global variable 'k' defined in
'test.c:7:12' (0x55a5cf268180) of size 120
0x55a5cf268184 is located 4 bytes to the right of global variable 's2' defined
in 'test.c:11:25' (0x55a5cf268100) of size 128
SUMMARY: AddressSanitizer: global-buffer-overflow
(/root/docker_share/csmith/gcc_self_10/g2.out+0x1200) in main
Shadow bytes around the buggy address:
0x0ab539e44fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab539e44ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab539e45000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab539e45010: 04 f9 f9 f9 f9 f9 f9 f9 05 f9 f9 f9 f9 f9 f9 f9
0x0ab539e45020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0ab539e45030:[f9]f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 f9
0x0ab539e45040: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab539e45050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab539e45060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab539e45070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab539e45080: 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
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c/99168] inconsistent behavior on -O0 and -O2 with ASAN on
2021-02-19 16:44 [Bug c/99168] New: inconsistent behavior on -O0 and -O2 with ASAN on zhan3299 at purdue dot edu
@ 2021-02-19 16:57 ` zhan3299 at purdue dot edu
2021-02-22 9:45 ` [Bug sanitizer/99168] " marxin at gcc dot gnu.org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: zhan3299 at purdue dot edu @ 2021-02-19 16:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99168
--- Comment #1 from zhan3299 at purdue dot edu ---
If we resolved the conflicts on "aligned", it would behave normally. I feel
like the ASAN is confused by the "aligned" somehow.
Should it have thrown some warnings?
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug sanitizer/99168] inconsistent behavior on -O0 and -O2 with ASAN on
2021-02-19 16:44 [Bug c/99168] New: inconsistent behavior on -O0 and -O2 with ASAN on zhan3299 at purdue dot edu
2021-02-19 16:57 ` [Bug c/99168] " zhan3299 at purdue dot edu
@ 2021-02-22 9:45 ` marxin at gcc dot gnu.org
2021-02-22 15:07 ` marxin at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: marxin at gcc dot gnu.org @ 2021-02-22 9:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99168
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
Ever confirmed|0 |1
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2021-02-22
--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
I'll take a look.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug sanitizer/99168] inconsistent behavior on -O0 and -O2 with ASAN on
2021-02-19 16:44 [Bug c/99168] New: inconsistent behavior on -O0 and -O2 with ASAN on zhan3299 at purdue dot edu
2021-02-19 16:57 ` [Bug c/99168] " zhan3299 at purdue dot edu
2021-02-22 9:45 ` [Bug sanitizer/99168] " marxin at gcc dot gnu.org
@ 2021-02-22 15:07 ` marxin at gcc dot gnu.org
2021-02-22 16:13 ` zhan3299 at purdue dot edu
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: marxin at gcc dot gnu.org @ 2021-02-22 15:07 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99168
--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Very interesting issue, the failure is caused by IPA ICF that merges 2
variables with different alignments. I've got a patch candidate.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug sanitizer/99168] inconsistent behavior on -O0 and -O2 with ASAN on
2021-02-19 16:44 [Bug c/99168] New: inconsistent behavior on -O0 and -O2 with ASAN on zhan3299 at purdue dot edu
` (2 preceding siblings ...)
2021-02-22 15:07 ` marxin at gcc dot gnu.org
@ 2021-02-22 16:13 ` zhan3299 at purdue dot edu
2021-02-22 16:44 ` marxin at gcc dot gnu.org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: zhan3299 at purdue dot edu @ 2021-02-22 16:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99168
--- Comment #4 from zhan3299 at purdue dot edu ---
(In reply to Martin Liška from comment #3)
> Very interesting issue, the failure is caused by IPA ICF that merges 2
> variables with different alignments. I've got a patch candidate.
Hi, just curious because I am also studying the source code of GCC.
Is this issue is about sanitizer or optimization?
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug sanitizer/99168] inconsistent behavior on -O0 and -O2 with ASAN on
2021-02-19 16:44 [Bug c/99168] New: inconsistent behavior on -O0 and -O2 with ASAN on zhan3299 at purdue dot edu
` (3 preceding siblings ...)
2021-02-22 16:13 ` zhan3299 at purdue dot edu
@ 2021-02-22 16:44 ` marxin at gcc dot gnu.org
2021-02-23 15:03 ` cvs-commit at gcc dot gnu.org
2021-02-23 15:05 ` marxin at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: marxin at gcc dot gnu.org @ 2021-02-22 16:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99168
--- Comment #5 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to zhan3299 from comment #4)
> (In reply to Martin Liška from comment #3)
> > Very interesting issue, the failure is caused by IPA ICF that merges 2
> > variables with different alignments. I've got a patch candidate.
>
> Hi, just curious because I am also studying the source code of GCC.
>
> Is this issue is about sanitizer or optimization?
It's bad optimization done by IPA ICF. The issue is gone with -fno-ipa-icf.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug sanitizer/99168] inconsistent behavior on -O0 and -O2 with ASAN on
2021-02-19 16:44 [Bug c/99168] New: inconsistent behavior on -O0 and -O2 with ASAN on zhan3299 at purdue dot edu
` (4 preceding siblings ...)
2021-02-22 16:44 ` marxin at gcc dot gnu.org
@ 2021-02-23 15:03 ` cvs-commit at gcc dot gnu.org
2021-02-23 15:05 ` marxin at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2021-02-23 15:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99168
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Liska <marxin@gcc.gnu.org>:
https://gcc.gnu.org/g:3f8384545784696fbd66aaec24a998a819e912c5
commit r11-7346-g3f8384545784696fbd66aaec24a998a819e912c5
Author: Martin Liska <mliska@suse.cz>
Date: Tue Feb 23 09:01:53 2021 +0100
IPA ICF + ASAN: do not merge vars with different alignment
gcc/ChangeLog:
PR sanitizer/99168
* ipa-icf.c (sem_variable::merge): Do not merge 2 variables
with different alignment. That leads to an invalid red zone
size allocated in runtime.
gcc/testsuite/ChangeLog:
PR sanitizer/99168
* c-c++-common/asan/pr99168.c: New test.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug sanitizer/99168] inconsistent behavior on -O0 and -O2 with ASAN on
2021-02-19 16:44 [Bug c/99168] New: inconsistent behavior on -O0 and -O2 with ASAN on zhan3299 at purdue dot edu
` (5 preceding siblings ...)
2021-02-23 15:03 ` cvs-commit at gcc dot gnu.org
@ 2021-02-23 15:05 ` marxin at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: marxin at gcc dot gnu.org @ 2021-02-23 15:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99168
Martin Liška <marxin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
--- Comment #7 from Martin Liška <marxin at gcc dot gnu.org> ---
Fixed on master.
^ permalink raw reply [flat|nested] 8+ messages in thread
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2021-02-22 9:45 ` [Bug sanitizer/99168] " marxin at gcc dot gnu.org
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