security_file_lock cmd argument

From: Sten Spans
Date: Thu Jul 09 2009 - 06:00:16 EST



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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