Since break_lease is called before i_writecount is incremented, there's
a window between the two where a setlease call would have no way to know
that an open is about to happen.
We fix this by adding a new inode field, i_blockleases, that is
incremented while a lease-breaking operation is in progress.
We will later reuse i_blockleases to enforce lease-breaking for rename,
unlink, etc.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
---
fs/inode.c | 1 +
fs/locks.c | 28 ++++++++++++++++++++++++++++
fs/namei.c | 6 +++++-
include/linux/fs.h | 3 +++
4 files changed, 37 insertions(+), 1 deletions(-)
diff --git a/fs/inode.c b/fs/inode.c
index 33c963d..4f253a2 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -198,6 +198,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
inode->i_uid = 0;
inode->i_gid = 0;
atomic_set(&inode->i_writecount, 0);
+ atomic_set(&inode->i_blockleases, 0);
inode->i_size = 0;
inode->i_blocks = 0;
inode->i_bytes = 0;
diff --git a/fs/locks.c b/fs/locks.c
index 0a4f50d..7699b1b 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1164,6 +1164,32 @@ static void time_out_leases(struct inode *inode)
}
}
+/* Disallow all leases (read or write): */
+void disallow_leases(struct inode *inode, int flags)
+{
+ if (!inode)
+ return;
+ if (!S_ISREG(inode->i_mode))
+ return;
+ if ((flags & O_ACCMODE) == O_RDONLY)
+ return;
+ atomic_inc(&inode->i_blockleases);
+}
+EXPORT_SYMBOL_GPL(disallow_leases);
+
+void reallow_leases(struct inode *inode, int flags)
+{
+ if (!inode)
+ return;
+ if (!S_ISREG(inode->i_mode))
+ return;
+ if ((flags & O_ACCMODE) == O_RDONLY)
+ return;
+ BUG_ON(atomic_read(&inode->i_blockleases) <= 0);
+ atomic_dec(&inode->i_blockleases);
+}
+EXPORT_SYMBOL_GPL(reallow_leases);
+
/**
* __break_lease - revoke all outstanding leases on file
* @inode: the inode of the file to return
@@ -1369,6 +1395,8 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
if (arg != F_UNLCK) {
error = -EAGAIN;
+ if (atomic_read(&inode->i_blockleases))
+ goto out;
if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
goto out;
if ((arg == F_WRLCK)
diff --git a/fs/namei.c b/fs/namei.c
index 3cb616d..079e68c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2277,10 +2277,14 @@ ok:
want_write = 1;
}
common:
+ disallow_leases(nd->path.dentry->d_inode, open_flag);
error = may_open(&nd->path, acc_mode, open_flag);
- if (error)
+ if (error) {
+ reallow_leases(nd->path.dentry->d_inode, open_flag);
goto exit;
+ }
filp = nameidata_to_filp(nd);
+ reallow_leases(nd->path.dentry->d_inode, open_flag);
if (!IS_ERR(filp)) {
error = ima_file_check(filp, op->acc_mode);
if (error) {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1b95af3..daf8443 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -796,6 +796,7 @@ struct inode {
#ifdef CONFIG_IMA
atomic_t i_readcount; /* struct files open RO */
#endif
+ atomic_t i_blockleases; /* setlease fails when >0 */
atomic_t i_writecount;
#ifdef CONFIG_SECURITY
void *i_security;
@@ -1161,6 +1162,8 @@ extern void lease_get_mtime(struct inode *, struct timespec *time);
extern int generic_setlease(struct file *, long, struct file_lock **);
extern int vfs_setlease(struct file *, long, struct file_lock **);
extern int lease_modify(struct file_lock **, int);
+extern void disallow_leases(struct inode *, int flags);
+extern void reallow_leases(struct inode *, int flags);
extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
extern void lock_flocks(void);
--
1.7.4.1
--
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