[PATCH 5.14 021/151] s390: fix strrchr() implementation

Greg Kroah-Hartman
2021-10-18T13:49:56Z

From: Roberto Sassu <roberto.sassu@huawei.com>

commit 8e0ab8e26b72a80e991c66a8abc16e6c856abe3d upstream.

Fix two problems found in the strrchr() implementation for s390
architectures: evaluate empty strings (return the string address instead of
NULL, if '\0' is passed as second argument); evaluate the first character
of non-empty strings (the current implementation stops at the second).

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Reported-by: Heiko Carstens <hca@linux.ibm.com> (incorrect behavior with empty strings)
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Link: https://lore.kernel.org/r/20211005120836.60630-1-roberto.sassu@huawei.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/s390/lib/string.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

--- a/arch/s390/lib/string.c
+++ b/arch/s390/lib/string.c
@@ -259,14 +259,13 @@ EXPORT_SYMBOL(strcmp);
#ifdef __HAVE_ARCH_STRRCHR
char *strrchr(const char *s, int c)
{
- size_t len = __strend(s) - s;
+ ssize_t len = __strend(s) - s;

- if (len)
- do {
- if (s[len] == (char) c)
- return (char *) s + len;
- } while (--len > 0);
- return NULL;
+ do {
+ if (s[len] == (char)c)
+ return (char *)s + len;
+ } while (--len >= 0);
+ return NULL;
}
EXPORT_SYMBOL(strrchr);
#endif