[Python-checkins] bpo-41524: fix pointer bug in PyOS_mystr{n}icmp (GH-21845)
wmeehan
webhook-mailer at python.org
Thu Aug 27 01:45:59 EDT 2020
https://github.com/python/cpython/commit/97eaf2b5e5c826b9abe59896a363853bef55c5d9
commit: 97eaf2b5e5c826b9abe59896a363853bef55c5d9
branch: master
author: wmeehan <wmeehan at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-08-27T14:45:25+09:00
summary:
bpo-41524: fix pointer bug in PyOS_mystr{n}icmp (GH-21845)
* bpo-41524: fix pointer bug in PyOS_mystr{n}icmp
The existing implementations of PyOS_mystrnicmp and PyOS_mystricmp
can increment pointers beyond the end of a string.
This commit fixes those cases by moving the mutation out of the condition.
* 📜🤖 Added by blurb_it.
* Address comments
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
files:
A Misc/NEWS.d/next/C API/2020-08-12-17-09-06.bpo-41524.u6Xfr2.rst
M Python/pystrcmp.c
diff --git a/Misc/NEWS.d/next/C API/2020-08-12-17-09-06.bpo-41524.u6Xfr2.rst b/Misc/NEWS.d/next/C API/2020-08-12-17-09-06.bpo-41524.u6Xfr2.rst
new file mode 100644
index 0000000000000..4704e29be29bb
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2020-08-12-17-09-06.bpo-41524.u6Xfr2.rst
@@ -0,0 +1,2 @@
+Fix bug in PyOS_mystrnicmp and PyOS_mystricmp that incremented
+pointers beyond the end of a string.
\ No newline at end of file
diff --git a/Python/pystrcmp.c b/Python/pystrcmp.c
index f9c2277cb56dc..9224ce4c70605 100644
--- a/Python/pystrcmp.c
+++ b/Python/pystrcmp.c
@@ -6,21 +6,25 @@
int
PyOS_mystrnicmp(const char *s1, const char *s2, Py_ssize_t size)
{
+ const unsigned char *p1, *p2;
if (size == 0)
return 0;
- while ((--size > 0) &&
- (tolower((unsigned)*s1) == tolower((unsigned)*s2))) {
- if (!*s1++ || !*s2++)
- break;
+ p1 = (const unsigned char *)s1;
+ p2 = (const unsigned char *)s2;
+ for (; (--size > 0) && *p1 && *p2 && (tolower(*p1) == tolower(*p2));
+ p1++, p2++) {
+ ;
}
- return tolower((unsigned)*s1) - tolower((unsigned)*s2);
+ return tolower(*p1) - tolower(*p2);
}
int
PyOS_mystricmp(const char *s1, const char *s2)
{
- while (*s1 && (tolower((unsigned)*s1++) == tolower((unsigned)*s2++))) {
+ const unsigned char *p1 = (const unsigned char *)s1;
+ const unsigned char *p2 = (const unsigned char *)s2;
+ for (; *p1 && *p2 && (tolower(*p1) == tolower(*p2)); p1++, p2++) {
;
}
- return (tolower((unsigned)*s1) - tolower((unsigned)*s2));
+ return (tolower(*p1) - tolower(*p2));
}
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