locks: fix file locking on overlayfs
This patch allows flock, posix locks, ofd locks and leases to work
correctly on overlayfs.
Instead of using the underlying inode for storing lock context use the
overlay inode. This allows locks to be persistent across copy-up.
This is done by introducing locks_inode() helper and using it instead of
file_inode() to get the inode in locking code. For non-overlayfs the two
are equivalent, except for an extra pointer dereference in locks_inode().
Since lock operations are in "struct file_operations" we must also make
sure not to call underlying filesystem's lock operations. Introcude a
super block flag MS_NOREMOTELOCK to this effect.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Jeff Layton <jlayton@poochiereds.net>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
diff --git a/fs/locks.c b/fs/locks.c
index ee1b15f..c1656cf 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -139,6 +139,11 @@
#define IS_LEASE(fl) (fl->fl_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
#define IS_OFDLCK(fl) (fl->fl_flags & FL_OFDLCK)
+static inline bool is_remote_lock(struct file *filp)
+{
+ return likely(!(filp->f_path.dentry->d_sb->s_flags & MS_NOREMOTELOCK));
+}
+
static bool lease_breaking(struct file_lock *fl)
{
return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
@@ -791,7 +796,7 @@
{
struct file_lock *cfl;
struct file_lock_context *ctx;
- struct inode *inode = file_inode(filp);
+ struct inode *inode = locks_inode(filp);
ctx = smp_load_acquire(&inode->i_flctx);
if (!ctx || list_empty_careful(&ctx->flc_posix)) {
@@ -1192,7 +1197,7 @@
int posix_lock_file(struct file *filp, struct file_lock *fl,
struct file_lock *conflock)
{
- return posix_lock_inode(file_inode(filp), fl, conflock);
+ return posix_lock_inode(locks_inode(filp), fl, conflock);
}
EXPORT_SYMBOL(posix_lock_file);
@@ -1232,7 +1237,7 @@
int locks_mandatory_locked(struct file *file)
{
int ret;
- struct inode *inode = file_inode(file);
+ struct inode *inode = locks_inode(file);
struct file_lock_context *ctx;
struct file_lock *fl;
@@ -1572,7 +1577,7 @@
int fcntl_getlease(struct file *filp)
{
struct file_lock *fl;
- struct inode *inode = file_inode(filp);
+ struct inode *inode = locks_inode(filp);
struct file_lock_context *ctx;
int type = F_UNLCK;
LIST_HEAD(dispose);
@@ -1580,7 +1585,7 @@
ctx = smp_load_acquire(&inode->i_flctx);
if (ctx && !list_empty_careful(&ctx->flc_lease)) {
spin_lock(&ctx->flc_lock);
- time_out_leases(file_inode(filp), &dispose);
+ time_out_leases(inode, &dispose);
list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
if (fl->fl_file != filp)
continue;
@@ -1628,7 +1633,7 @@
{
struct file_lock *fl, *my_fl = NULL, *lease;
struct dentry *dentry = filp->f_path.dentry;
- struct inode *inode = file_inode(filp);
+ struct inode *inode = dentry->d_inode;
struct file_lock_context *ctx;
bool is_deleg = (*flp)->fl_flags & FL_DELEG;
int error;
@@ -1742,7 +1747,7 @@
{
int error = -EAGAIN;
struct file_lock *fl, *victim = NULL;
- struct inode *inode = file_inode(filp);
+ struct inode *inode = locks_inode(filp);
struct file_lock_context *ctx;
LIST_HEAD(dispose);
@@ -1782,7 +1787,7 @@
int generic_setlease(struct file *filp, long arg, struct file_lock **flp,
void **priv)
{
- struct inode *inode = file_inode(filp);
+ struct inode *inode = locks_inode(filp);
int error;
if ((!uid_eq(current_fsuid(), inode->i_uid)) && !capable(CAP_LEASE))
@@ -1830,7 +1835,7 @@
int
vfs_setlease(struct file *filp, long arg, struct file_lock **lease, void **priv)
{
- if (filp->f_op->setlease)
+ if (filp->f_op->setlease && is_remote_lock(filp))
return filp->f_op->setlease(filp, arg, lease, priv);
else
return generic_setlease(filp, arg, lease, priv);
@@ -1979,7 +1984,7 @@
if (error)
goto out_free;
- if (f.file->f_op->flock)
+ if (f.file->f_op->flock && is_remote_lock(f.file))
error = f.file->f_op->flock(f.file,
(can_sleep) ? F_SETLKW : F_SETLK,
lock);
@@ -2005,7 +2010,7 @@
*/
int vfs_test_lock(struct file *filp, struct file_lock *fl)
{
- if (filp->f_op->lock)
+ if (filp->f_op->lock && is_remote_lock(filp))
return filp->f_op->lock(filp, F_GETLK, fl);
posix_test_lock(filp, fl);
return 0;
@@ -2129,7 +2134,7 @@
*/
int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
{
- if (filp->f_op->lock)
+ if (filp->f_op->lock && is_remote_lock(filp))
return filp->f_op->lock(filp, cmd, fl);
else
return posix_lock_file(filp, fl, conf);
@@ -2191,7 +2196,7 @@
if (file_lock == NULL)
return -ENOLCK;
- inode = file_inode(filp);
+ inode = locks_inode(filp);
/*
* This might block, so we do it before checking the inode.
@@ -2343,7 +2348,7 @@
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
- inode = file_inode(filp);
+ inode = locks_inode(filp);
/* Don't allow mandatory locks on files that may be memory mapped
* and shared.
@@ -2426,6 +2431,7 @@
void locks_remove_posix(struct file *filp, fl_owner_t owner)
{
int error;
+ struct inode *inode = locks_inode(filp);
struct file_lock lock;
struct file_lock_context *ctx;
@@ -2434,7 +2440,7 @@
* posix_lock_file(). Another process could be setting a lock on this
* file at the same time, but we wouldn't remove that lock anyway.
*/
- ctx = smp_load_acquire(&file_inode(filp)->i_flctx);
+ ctx = smp_load_acquire(&inode->i_flctx);
if (!ctx || list_empty(&ctx->flc_posix))
return;
@@ -2452,7 +2458,7 @@
if (lock.fl_ops && lock.fl_ops->fl_release_private)
lock.fl_ops->fl_release_private(&lock);
- trace_locks_remove_posix(file_inode(filp), &lock, error);
+ trace_locks_remove_posix(inode, &lock, error);
}
EXPORT_SYMBOL(locks_remove_posix);
@@ -2469,12 +2475,12 @@
.fl_type = F_UNLCK,
.fl_end = OFFSET_MAX,
};
- struct inode *inode = file_inode(filp);
+ struct inode *inode = locks_inode(filp);
if (list_empty(&flctx->flc_flock))
return;
- if (filp->f_op->flock)
+ if (filp->f_op->flock && is_remote_lock(filp))
filp->f_op->flock(filp, F_SETLKW, &fl);
else
flock_lock_inode(inode, &fl);
@@ -2508,7 +2514,7 @@
{
struct file_lock_context *ctx;
- ctx = smp_load_acquire(&file_inode(filp)->i_flctx);
+ ctx = smp_load_acquire(&locks_inode(filp)->i_flctx);
if (!ctx)
return;
@@ -2552,7 +2558,7 @@
*/
int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
{
- if (filp->f_op->lock)
+ if (filp->f_op->lock && is_remote_lock(filp))
return filp->f_op->lock(filp, F_CANCELLK, fl);
return 0;
}
@@ -2580,7 +2586,7 @@
fl_pid = fl->fl_pid;
if (fl->fl_file != NULL)
- inode = file_inode(fl->fl_file);
+ inode = locks_inode(fl->fl_file);
seq_printf(f, "%lld:%s ", id, pfx);
if (IS_POSIX(fl)) {
@@ -2682,7 +2688,7 @@
void show_fd_locks(struct seq_file *f,
struct file *filp, struct files_struct *files)
{
- struct inode *inode = file_inode(filp);
+ struct inode *inode = locks_inode(filp);
struct file_lock_context *ctx;
int id = 0;
diff --git a/fs/namespace.c b/fs/namespace.c
index 7bb2cda..dcd9afe 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2700,7 +2700,7 @@
flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
- MS_STRICTATIME);
+ MS_STRICTATIME | MS_NOREMOTELOCK);
if (flags & MS_REMOUNT)
retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
diff --git a/fs/open.c b/fs/open.c
index 4fd6e25..648fb9d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -726,7 +726,7 @@
if (error)
goto cleanup_all;
- error = break_lease(inode, f->f_flags);
+ error = break_lease(locks_inode(f), f->f_flags);
if (error)
goto cleanup_all;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index e2a94a2..3d0b9de 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1320,7 +1320,7 @@
sb->s_xattr = ovl_xattr_handlers;
sb->s_root = root_dentry;
sb->s_fs_info = ufs;
- sb->s_flags |= MS_POSIXACL;
+ sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK;
return 0;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7db097d6..8ee0f01 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1065,6 +1065,18 @@
extern void send_sigio(struct fown_struct *fown, int fd, int band);
+/*
+ * Return the inode to use for locking
+ *
+ * For overlayfs this should be the overlay inode, not the real inode returned
+ * by file_inode(). For any other fs file_inode(filp) and locks_inode(filp) are
+ * equal.
+ */
+static inline struct inode *locks_inode(const struct file *f)
+{
+ return f->f_path.dentry->d_inode;
+}
+
#ifdef CONFIG_FILE_LOCKING
extern int fcntl_getlk(struct file *, unsigned int, struct flock __user *);
extern int fcntl_setlk(unsigned int, struct file *, unsigned int,
@@ -1252,7 +1264,7 @@
static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
{
- return locks_lock_inode_wait(file_inode(filp), fl);
+ return locks_lock_inode_wait(locks_inode(filp), fl);
}
struct fasync_struct {
@@ -2155,7 +2167,7 @@
static inline int locks_verify_locked(struct file *file)
{
- if (mandatory_lock(file_inode(file)))
+ if (mandatory_lock(locks_inode(file)))
return locks_mandatory_locked(file);
return 0;
}
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 3b00f7c..2473272 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -132,6 +132,7 @@
#define MS_LAZYTIME (1<<25) /* Update the on-disk [acm]times lazily */
/* These sb flags are internal to the kernel */
+#define MS_NOREMOTELOCK (1<<27)
#define MS_NOSEC (1<<28)
#define MS_BORN (1<<29)
#define MS_ACTIVE (1<<30)
