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: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 11 insertions, 11 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index ae91dce8a547..4aa81e6ae067 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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))