From 9e8925b67a809bb27ce4b7d352d67f25cf1d7fc5 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Mon, 16 Nov 2015 09:49:34 -0500 Subject: [PATCH] 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 Cc: Dmitry Vyukov Cc: Jeff Layton Cc: J. Bruce Fields Signed-off-by: "Eric W. Biederman" Signed-off-by: Jeff Layton --- fs/Kconfig | 10 ++++++++ fs/locks.c | 2 ++ fs/namespace.c | 10 ++++++++ include/linux/fs.h | 74 +++++++++++++++++++++++++++++------------------------- 4 files changed, 62 insertions(+), 34 deletions(-) diff --git a/fs/Kconfig b/fs/Kconfig index da3f32f..59322e6 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -67,6 +67,16 @@ config FILE_LOCKING 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 @@ static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl) return error; } +#ifdef CONFIG_MANDATORY_FILE_LOCKING /** * locks_mandatory_locked - Check for an active lock * @file: the file to check @@ -1289,6 +1290,7 @@ int locks_mandatory_area(int read_write, struct inode *inode, } 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 @@ static inline bool may_mount(void) 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 @@ long do_mount(const char *dev_name, const char __user *dir_name, 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 @@ extern struct kobject *fs_kobj; #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 @@ static inline int locks_verify_truncate(struct inode *inode, 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 @@ static inline int break_layout(struct inode *inode, bool wait) } #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; -- 2.7.4