locks: Allow disabling mandatory locking at compile time
Mandatory locking appears to be almost unused and buggy and there
appears no real interest in doing anything with it. Since effectively
no one uses the code and since the code is buggy let's allow it to be
disabled at compile time. I would just suggest removing the code but
undoubtedly that will break some piece of userspace code somewhere.
For the distributions that don't care about this piece of code
this gives a nice starting point to make mandatory locking go away.
Cc: Benjamin Coddington <bcodding@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Jeff Layton <jeff.layton@primarydata.com>
Cc: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
diff --git a/fs/Kconfig b/fs/Kconfig
index da3f32f..59322e6 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -67,6 +67,16 @@
for filesystems like NFS and for the flock() system
call. Disabling this option saves about 11k.
+config MANDATORY_FILE_LOCKING
+ bool "Enable Mandatory file locking"
+ depends on FILE_LOCKING
+ default y
+ help
+ This option enables files appropriately marked files on appropriely
+ mounted filesystems to support mandatory locking.
+
+ To the best of my knowledge this is dead code that no one cares about.
+
source "fs/notify/Kconfig"
source "fs/quota/Kconfig"
diff --git a/fs/locks.c b/fs/locks.c
index 0d2b326..86c9467 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1191,6 +1191,7 @@
return error;
}
+#ifdef CONFIG_MANDATORY_FILE_LOCKING
/**
* locks_mandatory_locked - Check for an active lock
* @file: the file to check
@@ -1289,6 +1290,7 @@
}
EXPORT_SYMBOL(locks_mandatory_area);
+#endif /* CONFIG_MANDATORY_FILE_LOCKING */
static void lease_clear_pending(struct file_lock *fl, int arg)
{
diff --git a/fs/namespace.c b/fs/namespace.c
index 0570729..4219885 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1584,6 +1584,14 @@
return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
}
+static inline bool may_mandlock(void)
+{
+#ifndef CONFIG_MANDATORY_FILE_LOCKING
+ return false;
+#endif
+ return true;
+}
+
/*
* Now umount can handle mount points as well as block devices.
* This is important for filesystems which use unnamed block devices.
@@ -2677,6 +2685,8 @@
type_page, flags, data_page);
if (!retval && !may_mount())
retval = -EPERM;
+ if (!retval && (flags & MS_MANDLOCK) && !may_mandlock())
+ retval = -EPERM;
if (retval)
goto dput_out;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3aa5142..cbf08d5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2030,7 +2030,7 @@
#define FLOCK_VERIFY_READ 1
#define FLOCK_VERIFY_WRITE 2
-#ifdef CONFIG_FILE_LOCKING
+#ifdef CONFIG_MANDATORY_FILE_LOCKING
extern int locks_mandatory_locked(struct file *);
extern int locks_mandatory_area(int, struct inode *, struct file *, loff_t, size_t);
@@ -2075,6 +2075,45 @@
return 0;
}
+#else /* !CONFIG_MANDATORY_FILE_LOCKING */
+
+static inline int locks_mandatory_locked(struct file *file)
+{
+ return 0;
+}
+
+static inline int locks_mandatory_area(int rw, struct inode *inode,
+ struct file *filp, loff_t offset,
+ size_t count)
+{
+ return 0;
+}
+
+static inline int __mandatory_lock(struct inode *inode)
+{
+ return 0;
+}
+
+static inline int mandatory_lock(struct inode *inode)
+{
+ return 0;
+}
+
+static inline int locks_verify_locked(struct file *file)
+{
+ return 0;
+}
+
+static inline int locks_verify_truncate(struct inode *inode, struct file *filp,
+ size_t size)
+{
+ return 0;
+}
+
+#endif /* CONFIG_MANDATORY_FILE_LOCKING */
+
+
+#ifdef CONFIG_FILE_LOCKING
static inline int break_lease(struct inode *inode, unsigned int mode)
{
/*
@@ -2136,39 +2175,6 @@
}
#else /* !CONFIG_FILE_LOCKING */
-static inline int locks_mandatory_locked(struct file *file)
-{
- return 0;
-}
-
-static inline int locks_mandatory_area(int rw, struct inode *inode,
- struct file *filp, loff_t offset,
- size_t count)
-{
- return 0;
-}
-
-static inline int __mandatory_lock(struct inode *inode)
-{
- return 0;
-}
-
-static inline int mandatory_lock(struct inode *inode)
-{
- return 0;
-}
-
-static inline int locks_verify_locked(struct file *file)
-{
- return 0;
-}
-
-static inline int locks_verify_truncate(struct inode *inode, struct file *filp,
- size_t size)
-{
- return 0;
-}
-
static inline int break_lease(struct inode *inode, unsigned int mode)
{
return 0;