linux-kernel - security_file

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Date:	Thu, 9 Jul 2009 11:45:44 +0200
From:	Sten Spans <Sten_Spans@...ua.de>
To:	linux-kernel@...r.kernel.org
Subject: security_file_lock cmd argument

I was playing around with the security_file_lock hook which
is invoked from fs/locks.c. The desciption in include/linux/security.h
states the following:

 * @file_lock:
 *      Check permission before performing file locking operations.
 *      Note: this hook mediates both flock and fcntl style locks.
 *      @file contains the file structure.
 *      @cmd contains the posix-translated lock operation to perform
 *      (e.g. F_RDLCK, F_WRLCK).

However when invoked via sys_flock:

SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
{
..
        error = security_file_lock(filp, cmd);

Which results in passing flock style arguments (LOCK_*) rather
than fcntl (F_*LCK). This also is inconsistent with the two
other security_file_lock invocations in the same file.
This one-liner fixes the issue:

--- fs/locks.c.orig	2009-07-09 11:26:45.000000000 +0200
+++ fs/locks.c	2009-07-09 11:27:24.000000000 +0200
@@ -1590,7 +1590,7 @@
 	if (can_sleep)
 		lock->fl_flags |= FL_SLEEP;

-	error = security_file_lock(filp, cmd);
+	error = security_file_lock(filp, lock->fl_type);
 	if (error)
 		goto out_free;

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