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* [Bug sanitizer/105084] New: ASAN false positive on global-buffer-overflow
@ 2022-03-28 15:35 shaohua.li at inf dot ethz.ch
2022-03-28 15:40 ` [Bug sanitizer/105084] " shaohua.li at inf dot ethz.ch
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2022-03-28 15:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105084
Bug ID: 105084
Summary: ASAN false positive on global-buffer-overflow
Product: gcc
Version: 12.0
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: ---
Hi,
ASAN seems to falsely report global-buffer-overflow with "-O1" and above. I
tested with gcc trunk, 11.0, 10.0, and 9.0. They all reported the same issue. I
wonder if this behaviour is intended or not. For clang's ASAN, it does not
report anything on the program.
$
$cat a.c
int a[] = {3};
int b = 7;
main() {
unsigned int *c = &b;
*c = a[1];
}
$
$gcc -fsanitize=address -w -O0; ./a.out
$
$gcc -fsanitize=address -w -O1; ./a.out
==292501==ERROR: AddressSanitizer: global-buffer-overflow on address
0x55aff123e040 at pc 0x55aff123b218 bp 0x7ffd41151fd0 sp 0x7ffd41151fc0
READ of size 4 at 0x55aff123e040 thread T0
#0 0x55aff123b217 in main (/shared/oob/debug_wrong3/a.out+0x2217)
#1 0x7f3933a360b2 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x240b2)
#2 0x55aff123b10d in _start (/shared/oob/debug_wrong3/a.out+0x210d)
0x55aff123e040 is located 32 bytes to the left of global variable 'ak' defined
in 'simple.c:26:16' (0x55aff123e060) of size 4
0x55aff123e040 is located 28 bytes to the right of global variable 'al' defined
in 'simple.c:27:16' (0x55aff123e020) of size 4
SUMMARY: AddressSanitizer: global-buffer-overflow
(/shared/oob/debug_wrong3/a.out+0x2217) in main
Shadow bytes around the buggy address:
0x0ab67e23fbb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab67e23fbc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab67e23fbd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab67e23fbe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab67e23fbf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0ab67e23fc00: 00 00 00 00 04 f9 f9 f9[f9]f9 f9 f9 04 f9 f9 f9
0x0ab67e23fc10: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab67e23fc20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab67e23fc30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0ab67e23fc40: 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9 f9
0x0ab67e23fc50: 04 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug sanitizer/105084] ASAN false positive on global-buffer-overflow
2022-03-28 15:35 [Bug sanitizer/105084] New: ASAN false positive on global-buffer-overflow shaohua.li at inf dot ethz.ch
@ 2022-03-28 15:40 ` shaohua.li at inf dot ethz.ch
2022-03-28 16:03 ` jakub at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2022-03-28 15:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105084
--- Comment #1 from Li Shaohua <shaohua.li at inf dot ethz.ch> ---
Sorry, the triggering program should be the following:
$cat a.c
int a[] = {3};
int b = 7;
main() {
unsigned int *c = &b;
*c = a[-1];
}
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug sanitizer/105084] ASAN false positive on global-buffer-overflow
2022-03-28 15:35 [Bug sanitizer/105084] New: ASAN false positive on global-buffer-overflow shaohua.li at inf dot ethz.ch
2022-03-28 15:40 ` [Bug sanitizer/105084] " shaohua.li at inf dot ethz.ch
@ 2022-03-28 16:03 ` jakub at gcc dot gnu.org
2022-03-28 20:19 ` shaohua.li at inf dot ethz.ch
2022-03-29 7:17 ` rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-03-28 16:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105084
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Neither is false positive, both are real bugs in your test programs.
The fact that on the second testcase a violation isn't reported at -O0 and is
at -O2 depends on the ordering of the global variables (we emit a then b for
-O0 and b then a for -O2).
We only emit the red zones after each variable, not both before and after each
var, because that would waste too much memory especially in programs that use a
lot of translation units and very few global vars in each.
If all the translation units in a program (or shared library) are compiled with
-fsanitize=address, the net effect is that underflows for the first variable
(probably in each section variables are present) aren't detected, when mixing
-fsanitize=address and non-sanitized objects it can result in more underflows
not being detected.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug sanitizer/105084] ASAN false positive on global-buffer-overflow
2022-03-28 15:35 [Bug sanitizer/105084] New: ASAN false positive on global-buffer-overflow shaohua.li at inf dot ethz.ch
2022-03-28 15:40 ` [Bug sanitizer/105084] " shaohua.li at inf dot ethz.ch
2022-03-28 16:03 ` jakub at gcc dot gnu.org
@ 2022-03-28 20:19 ` shaohua.li at inf dot ethz.ch
2022-03-29 7:17 ` rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2022-03-28 20:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105084
--- Comment #3 from Li Shaohua <shaohua.li at inf dot ethz.ch> ---
Thanks a lot for your explanation. That makes sense to me :).
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug sanitizer/105084] ASAN false positive on global-buffer-overflow
2022-03-28 15:35 [Bug sanitizer/105084] New: ASAN false positive on global-buffer-overflow shaohua.li at inf dot ethz.ch
` (2 preceding siblings ...)
2022-03-28 20:19 ` shaohua.li at inf dot ethz.ch
@ 2022-03-29 7:17 ` rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-03-29 7:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105084
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|UNCONFIRMED |RESOLVED
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-03-29 7:17 UTC | newest]
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2022-03-28 15:35 [Bug sanitizer/105084] New: ASAN false positive on global-buffer-overflow shaohua.li at inf dot ethz.ch
2022-03-28 15:40 ` [Bug sanitizer/105084] " shaohua.li at inf dot ethz.ch
2022-03-28 16:03 ` jakub at gcc dot gnu.org
2022-03-28 20:19 ` shaohua.li at inf dot ethz.ch
2022-03-29 7:17 ` rguenth at gcc dot gnu.org
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