From: Sergiy Kibrik <sakib@meta.ua>
Date: Tue, 18 Aug 2015 06:28:39 +0000 (+0300)
Subject: ulog: avoid accidental /dev/kmsg creation
X-Git-Url: http://git.openwrt.org/?p=project%2Flibubox.git;a=commitdiff_plain;h=136a5196266d03d537f822c4e67d2fde2ed59505

ulog: avoid accidental /dev/kmsg creation

Race is possible in ulog_kmsg(): if no /dev/kmsg exists
(e.g. while /dev gets re-mounted) regular file created instead.
>From this point system goes without kernel logger:
special character file can't be created anymore, all clients keep
overwriting single message in regular file.

To avoid this we open file in "r+" mode which doesn't create
file if it's not found.

Signed-off-by: Sergiy Kibrik <sakib@meta.ua>
Cc: John Crispin <blogic@openwrt.org>
---

diff --git a/ulog.c b/ulog.c
index 66aad90..296605d 100644
--- a/ulog.c
+++ b/ulog.c
@@ -90,7 +90,7 @@ static void ulog_kmsg(int priority, const char *fmt, va_list ap)
 {
 	FILE *kmsg;
 
-	if ((kmsg = fopen("/dev/kmsg", "w")) != NULL) {
+	if ((kmsg = fopen("/dev/kmsg", "r+")) != NULL) {
 		fprintf(kmsg, "<%u>", priority);
 
 		if (_ulog_ident)