linux-kernel - [PATCH v2] s390: Fix strrchr() implementation

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Message-ID: <20211005120836.60630-1-roberto.sassu@huawei.com>
Date:   Tue, 5 Oct 2021 14:08:36 +0200
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     <hca@...ux.ibm.com>, <gor@...ux.ibm.com>, <borntraeger@...ibm.com>
CC:     <linux-s390@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Roberto Sassu <roberto.sassu@...wei.com>,
        <stable@...r.kernel.org>
Subject: [PATCH v2] s390: Fix strrchr() implementation

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@...r.kernel.org
Reported-by: Heiko Carstens <hca@...ux.ibm.com> (incorrect behavior with empty strings)
Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 arch/s390/lib/string.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/s390/lib/string.c b/arch/s390/lib/string.c
index cfcdf76d6a95..8127e110d154 100644
--- 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;
-
-       if (len)
-	       do {
-		       if (s[len] == (char) c)
-			       return (char *) s + len;
-	       } while (--len > 0);
-       return NULL;
+	size_t len = __strend(s) - s;
+
+	do {
+		if (s[len] == (char) c)
+			return (char *) s + len;
+	} while (--len >= 0);
+	return NULL;
 }
 EXPORT_SYMBOL(strrchr);
 #endif
-- 
2.32.0