https://bugs.kde.org/show_bug.cgi?id=452072
Bug ID: 452072
Summary: false positive from wmemcmp_avx2_movbe (glibc-2.34 or
later?)
Product: valgrind
Version: 3.18.1
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: memcheck
Assignee: jsew...@acm.org
Reporter: takimot...@kba.biglobe.ne.jp
Target Milestone: ---
Created attachment 147840
--> https://bugs.kde.org/attachment.cgi?id=147840&action=edit
output of "valgrind -v ./a.out"
SUMMARY
wmemcmp(s1, s2, n) gives false positive even if n is smaller than the allocated
size of s1 and s2
STEPS TO REPRODUCE
1. compile the following C source (test.c):
#include <stdlib.h>
#include <wchar.h>
int main() {
wchar_t *a, *b;
int ret;
a = (wchar_t*)calloc(3, sizeof(wchar_t));
b = (wchar_t*)calloc(3, sizeof(wchar_t));
ret = wmemcmp(a, b, 2);
free(a);
free(b);
return ret;
}
2. valgrind ./a.out
OBSERVED RESULT
Invalid read of size 32
at 0x49EB499: __wmemcmp_avx2_movbe (memcmp-avx2-movbe.S:412)
by 0x40118B: main (test.c:8)
Address 0x4a75090 is 0 bytes inside a block of size 12 alloc'd
at 0x4849464: calloc (vg_replace_malloc.c:1328)
by 0x40116F: main (test.c:7)
Output of 'valglind -v ./a.out' is in log.txt.
EXPECTED RESULT
no error
SOFTWARE/OS VERSIONS
Fedora-35
ADDITIONAL INFORMATION
CPU is x86_64 with AVX2.
Fedora-35 uses glibc-2.34.
Same problem in the latest Arch Linux (glibc-2.35),
but no problem in Fedora-34 (glibc-2.33).
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