Commit d7a06983 authored by Jeff Layton's avatar Jeff Layton
Browse files

locks: fix locks_mandatory_locked to respect file-private locks 



As Trond pointed out, you can currently deadlock yourself by setting a
file-private lock on a file that requires mandatory locking and then
trying to do I/O on it.

Avoid this problem by plumbing some knowledge of file-private locks into
the mandatory locking code. In order to do this, we must pass down
information about the struct file that's being used to
locks_verify_locked.

Reported-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
Acked-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 90478939

fs/locks.c

+4 −3
Original line number Diff line number Diff line
@@ -1155,13 +1155,14 @@ EXPORT_SYMBOL(posix_lock_file_wait); 


/**

 * locks_mandatory_locked - Check for an active lock

 * @inode: the file to check

 * @file: the file to check

 *

 * Searches the inode's list of locks to find any POSIX locks which conflict.

 * This function is called from locks_verify_locked() only.

 */

int locks_mandatory_locked(struct inode *inode)

int locks_mandatory_locked(struct file *file)

{

	struct inode *inode = file_inode(file);

	fl_owner_t owner = current->files;

	struct file_lock *fl;
@@ -1172,7 +1173,7 @@ int locks_mandatory_locked(struct inode *inode) 
	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {

		if (!IS_POSIX(fl))

			continue;

		if (fl->fl_owner != owner)

		if (fl->fl_owner != owner && fl->fl_owner != (fl_owner_t)file)

			break;

	}

	spin_unlock(&inode->i_lock);

fs/namei.c

+1 −1
Original line number Diff line number Diff line
@@ -2542,7 +2542,7 @@ static int handle_truncate(struct file *filp) 
	/*

	 * Refuse to truncate files with mandatory locks held on them.

	 */

	error = locks_verify_locked(inode);

	error = locks_verify_locked(filp);

	if (!error)

		error = security_path_truncate(path);

	if (!error) {

include/linux/fs.h

+11 −11
Original line number Diff line number Diff line
@@ -1912,6 +1912,11 @@ extern int current_umask(void); 
extern void ihold(struct inode * inode);

extern void iput(struct inode *);



static inline struct inode *file_inode(struct file *f)

{

	return f->f_inode;

}



/* /sys/fs */

extern struct kobject *fs_kobj;
@@ -1921,7 +1926,7 @@ extern struct kobject *fs_kobj; 
#define FLOCK_VERIFY_WRITE 2



#ifdef CONFIG_FILE_LOCKING

extern int locks_mandatory_locked(struct inode *);

extern int locks_mandatory_locked(struct file *);

extern int locks_mandatory_area(int, struct inode *, struct file *, loff_t, size_t);



/*
@@ -1944,10 +1949,10 @@ static inline int mandatory_lock(struct inode *ino) 
	return IS_MANDLOCK(ino) && __mandatory_lock(ino);

}



static inline int locks_verify_locked(struct inode *inode)

static inline int locks_verify_locked(struct file *file)

{

	if (mandatory_lock(inode))

		return locks_mandatory_locked(inode);

	if (mandatory_lock(file_inode(file)))

		return locks_mandatory_locked(file);

	return 0;

}
@@ -2008,7 +2013,7 @@ static inline int break_deleg_wait(struct inode **delegated_inode) 
}



#else /* !CONFIG_FILE_LOCKING */

static inline int locks_mandatory_locked(struct inode *inode)

static inline int locks_mandatory_locked(struct file *file)

{

	return 0;

}
@@ -2030,7 +2035,7 @@ static inline int mandatory_lock(struct inode *inode) 
	return 0;

}



static inline int locks_verify_locked(struct inode *inode)

static inline int locks_verify_locked(struct file *file)

{

	return 0;

}
@@ -2297,11 +2302,6 @@ static inline bool execute_ok(struct inode *inode) 
	return (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode);

}



static inline struct inode *file_inode(struct file *f)

{

	return f->f_inode;

}



static inline void file_start_write(struct file *file)

{

	if (!S_ISREG(file_inode(file)->i_mode))

mm/mmap.c

+1 −1
Original line number Diff line number Diff line
@@ -1299,7 +1299,7 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, 
			/*

			 * Make sure there are no mandatory locks on the file.

			 */

			if (locks_verify_locked(inode))

			if (locks_verify_locked(file))

				return -EAGAIN;



			vm_flags |= VM_SHARED | VM_MAYSHARE;

mm/nommu.c

+1 −1
Original line number Diff line number Diff line
@@ -995,7 +995,7 @@ static int validate_mmap_request(struct file *file, 
			    (file->f_mode & FMODE_WRITE))

				return -EACCES;



			if (locks_verify_locked(file_inode(file)))

			if (locks_verify_locked(file))

				return -EAGAIN;



			if (!(capabilities & BDI_CAP_MAP_DIRECT))

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