linux-kernel - [PATCH 40/44] kdbus: Cleanup kdbus_item_validate

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Message-Id: <04429ba8051ff804a932cba201d70ca614dc2b49.1444302968.git.sergei@s15v.net>
Date:	Thu,  8 Oct 2015 14:32:09 +0300
From:	Sergei Zviagintsev <sergei@...v.net>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...glemail.com>,
	Djalal Harouni <tixxdz@...ndz.org>
Cc:	linux-kernel@...r.kernel.org, Sergei Zviagintsev <sergei@...v.net>
Subject: [PATCH 40/44] kdbus: Cleanup kdbus_item_validate_name()

Calculate length of the string directly from item's payload size and
simplify tests. Do not use strlen(), as kdbus_str_valid() guarantees
that '\0' is located in the end of provided buffer. When examining
contents of the string, use pointer instead of array index to stay more
concise and readable.

Signed-off-by: Sergei Zviagintsev <sergei@...v.net>
---
 ipc/kdbus/item.c | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/ipc/kdbus/item.c b/ipc/kdbus/item.c
index ce78dba03426..e6b6e2ca7e05 100644
--- a/ipc/kdbus/item.c
+++ b/ipc/kdbus/item.c
@@ -37,32 +37,26 @@ static bool kdbus_str_valid(const char *str, size_t size)
  */
 int kdbus_item_validate_name(const struct kdbus_item *item)
 {
-	const char *name = item->str;
-	unsigned int i;
-	size_t len;
+	const char *p, *name = item->str;
+	size_t len = KDBUS_ITEM_PAYLOAD_SIZE(item) - 1;
 
-	if (item->size < KDBUS_ITEM_HEADER_SIZE + 2)
+	if (len > item->size || len < 1)
 		return -EINVAL;
 
-	if (item->size > KDBUS_ITEM_HEADER_SIZE +
-			 KDBUS_SYSNAME_MAX_LEN + 1)
+	if (len > KDBUS_SYSNAME_MAX_LEN)
 		return -ENAMETOOLONG;
 
-	if (!kdbus_str_valid(name, KDBUS_ITEM_PAYLOAD_SIZE(item)))
+	if (!kdbus_str_valid(name, len + 1))
 		return -EINVAL;
 
-	len = strlen(name);
-	if (len == 0)
-		return -EINVAL;
-
-	for (i = 0; i < len; i++) {
-		if (isalpha(name[i]))
+	for (p = name; *p; ++p) {
+		if (isalpha(*p))
 			continue;
-		if (isdigit(name[i]))
+		if (isdigit(*p))
 			continue;
-		if (name[i] == '_')
+		if (*p == '_')
 			continue;
-		if (i > 0 && i + 1 < len && (name[i] == '-' || name[i] == '.'))
+		if (p > name && *(p + 1) && (*p == '-' || *p == '.'))
 			continue;
 
 		return -EINVAL;
-- 
1.8.3.1

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