linux-kernel - [PATCH] check_syslog

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Date:	Sat, 30 May 2015 16:51:55 +0300
From:	Vasily Averin <vvs@...tuozzo.com>
To:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Kees Cook <keescook@...omium.org>, Josh Boyer <jwboyer@...hat.com>,
	Eric Paris <eparis@...hat.com>
Subject: [PATCH] check_syslog_permissions() cleanup

Patch fixes drawbacks in heck_syslog_permissions() noticed by AKPM:
"from_file handling makes me cry.

That's not a boolean - it's an enumerated value with two values
currently defined.

But the code in check_syslog_permissions() treats it as a boolean and
also hardwires the knowledge that SYSLOG_FROM_PROC == 1 (or == `true`).

And the name is wrong: it should be called from_proc to match
SYSLOG_FROM_PROC."

Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
---
 include/linux/syslog.h |  6 +++---
 kernel/printk/printk.c | 10 +++++-----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/syslog.h b/include/linux/syslog.h
index 4b7b875..c3a7f0c 100644
--- a/include/linux/syslog.h
+++ b/include/linux/syslog.h
@@ -47,12 +47,12 @@
 #define SYSLOG_FROM_READER           0
 #define SYSLOG_FROM_PROC             1
 
-int do_syslog(int type, char __user *buf, int count, bool from_file);
+int do_syslog(int type, char __user *buf, int count, int source);
 
 #ifdef CONFIG_PRINTK
-int check_syslog_permissions(int type, bool from_file);
+int check_syslog_permissions(int type, int source);
 #else
-static inline int check_syslog_permissions(int type, bool from_file)
+static inline int check_syslog_permissions(int type, int source)
 {
 	return 0;
 }
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index bff0169..5ed9d6d 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -477,13 +477,13 @@ static int syslog_action_restricted(int type)
 	       type != SYSLOG_ACTION_SIZE_BUFFER;
 }
 
-int check_syslog_permissions(int type, bool from_file)
+int check_syslog_permissions(int type, int source)
 {
 	/*
 	 * If this is from /proc/kmsg and we've already opened it, then we've
 	 * already done the capabilities checks at open time.
 	 */
-	if (from_file && type != SYSLOG_ACTION_OPEN)
+	if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
 		goto ok;
 
 	if (syslog_action_restricted(type)) {
@@ -1254,13 +1254,13 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
 	return len;
 }
 
-int do_syslog(int type, char __user *buf, int len, bool from_file)
+int do_syslog(int type, char __user *buf, int len, int source)
 {
 	bool clear = false;
 	static int saved_console_loglevel = LOGLEVEL_DEFAULT;
 	int error;
 
-	error = check_syslog_permissions(type, from_file);
+	error = check_syslog_permissions(type, source);
 	if (error)
 		goto out;
 
@@ -1343,7 +1343,7 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
 			syslog_prev = 0;
 			syslog_partial = 0;
 		}
-		if (from_file) {
+		if (source == SYSLOG_FROM_PROC) {
 			/*
 			 * Short-cut for poll(/"proc/kmsg") which simply checks
 			 * for pending data, not the size; return the count of
-- 
1.9.1

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