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authorAl Viro <viro@zeniv.linux.org.uk>2010-04-30 17:17:09 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2010-05-15 07:16:33 -0400
commitd83c49f3e36cecd2e8823b6c48ffba083b8a5704 (patch)
treea304de4eb43652d2a9528d4b43f798ab821c8b93
parent6a251b0ab67989f468f4cb65179e0cf40cf8c295 (diff)
Fix the regression created by "set S_DEAD on unlink()..." commit
1) i_flags simply doesn't work for mount/unlink race prevention; we may have many links to file and rm on one of those obviously shouldn't prevent bind on top of another later on. To fix it right way we need to mark _dentry_ as unsuitable for mounting upon; new flag (DCACHE_CANT_MOUNT) is protected by d_flags and i_mutex on the inode in question. Set it (with dont_mount(dentry)) in unlink/rmdir/etc., check (with cant_mount(dentry)) in places in namespace.c that used to check for S_DEAD. Setting S_DEAD is still needed in places where we used to set it (for directories getting killed), since we rely on it for readdir/rmdir race prevention. 2) rename()/mount() protection has another bogosity - we unhash the target before we'd checked that it's not a mountpoint. Fixed. 3) ancient bogosity in pivot_root() - we locked i_mutex on the right directory, but checked S_DEAD on the different (and wrong) one. Noticed and fixed. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--drivers/usb/core/inode.c1
-rw-r--r--fs/configfs/dir.c4
-rw-r--r--fs/namei.c21
-rw-r--r--fs/namespace.c6
-rw-r--r--include/linux/dcache.h14
5 files changed, 35 insertions, 11 deletions
diff --git a/drivers/usb/core/inode.c b/drivers/usb/core/inode.c
index 4a6366a4212..111a01a747f 100644
--- a/drivers/usb/core/inode.c
+++ b/drivers/usb/core/inode.c
@@ -380,6 +380,7 @@ static int usbfs_rmdir(struct inode *dir, struct dentry *dentry)
mutex_lock(&inode->i_mutex);
dentry_unhash(dentry);
if (usbfs_empty(dentry)) {
+ dont_mount(dentry);
drop_nlink(dentry->d_inode);
drop_nlink(dentry->d_inode);
dput(dentry);
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 8e48b52205a..0b502f80c69 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -645,6 +645,7 @@ static void detach_groups(struct config_group *group)
configfs_detach_group(sd->s_element);
child->d_inode->i_flags |= S_DEAD;
+ dont_mount(child);
mutex_unlock(&child->d_inode->i_mutex);
@@ -840,6 +841,7 @@ static int configfs_attach_item(struct config_item *parent_item,
mutex_lock(&dentry->d_inode->i_mutex);
configfs_remove_dir(item);
dentry->d_inode->i_flags |= S_DEAD;
+ dont_mount(dentry);
mutex_unlock(&dentry->d_inode->i_mutex);
d_delete(dentry);
}
@@ -882,6 +884,7 @@ static int configfs_attach_group(struct config_item *parent_item,
if (ret) {
configfs_detach_item(item);
dentry->d_inode->i_flags |= S_DEAD;
+ dont_mount(dentry);
}
configfs_adjust_dir_dirent_depth_after_populate(sd);
mutex_unlock(&dentry->d_inode->i_mutex);
@@ -1725,6 +1728,7 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
mutex_unlock(&configfs_symlink_mutex);
configfs_detach_group(&group->cg_item);
dentry->d_inode->i_flags |= S_DEAD;
+ dont_mount(dentry);
mutex_unlock(&dentry->d_inode->i_mutex);
d_delete(dentry);
diff --git a/fs/namei.c b/fs/namei.c
index 16df7277a92..b86b96fe1dc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2176,8 +2176,10 @@ int vfs_rmdir(struct inode *dir, struct dentry *dentry)
error = security_inode_rmdir(dir, dentry);
if (!error) {
error = dir->i_op->rmdir(dir, dentry);
- if (!error)
+ if (!error) {
dentry->d_inode->i_flags |= S_DEAD;
+ dont_mount(dentry);
+ }
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
@@ -2261,7 +2263,7 @@ int vfs_unlink(struct inode *dir, struct dentry *dentry)
if (!error) {
error = dir->i_op->unlink(dir, dentry);
if (!error)
- dentry->d_inode->i_flags |= S_DEAD;
+ dont_mount(dentry);
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
@@ -2572,17 +2574,20 @@ static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
return error;
target = new_dentry->d_inode;
- if (target) {
+ if (target)
mutex_lock(&target->i_mutex);
- dentry_unhash(new_dentry);
- }
if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
error = -EBUSY;
- else
+ else {
+ if (target)
+ dentry_unhash(new_dentry);
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
+ }
if (target) {
- if (!error)
+ if (!error) {
target->i_flags |= S_DEAD;
+ dont_mount(new_dentry);
+ }
mutex_unlock(&target->i_mutex);
if (d_unhashed(new_dentry))
d_rehash(new_dentry);
@@ -2614,7 +2619,7 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
if (!error) {
if (target)
- target->i_flags |= S_DEAD;
+ dont_mount(new_dentry);
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
d_move(old_dentry, new_dentry);
}
diff --git a/fs/namespace.c b/fs/namespace.c
index 8174c8ab5c7..f20cb57d106 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1432,7 +1432,7 @@ static int graft_tree(struct vfsmount *mnt, struct path *path)
err = -ENOENT;
mutex_lock(&path->dentry->d_inode->i_mutex);
- if (IS_DEADDIR(path->dentry->d_inode))
+ if (cant_mount(path->dentry))
goto out_unlock;
err = security_sb_check_sb(mnt, path);
@@ -1623,7 +1623,7 @@ static int do_move_mount(struct path *path, char *old_name)
err = -ENOENT;
mutex_lock(&path->dentry->d_inode->i_mutex);
- if (IS_DEADDIR(path->dentry->d_inode))
+ if (cant_mount(path->dentry))
goto out1;
if (d_unlinked(path->dentry))
@@ -2234,7 +2234,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
if (!check_mnt(root.mnt))
goto out2;
error = -ENOENT;
- if (IS_DEADDIR(new.dentry->d_inode))
+ if (cant_mount(old.dentry))
goto out2;
if (d_unlinked(new.dentry))
goto out2;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 30b93b2a01a..eebb617c17d 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -186,6 +186,8 @@ d_iput: no no no yes
#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */
+#define DCACHE_CANT_MOUNT 0x0100
+
extern spinlock_t dcache_lock;
extern seqlock_t rename_lock;
@@ -358,6 +360,18 @@ static inline int d_unlinked(struct dentry *dentry)
return d_unhashed(dentry) && !IS_ROOT(dentry);
}
+static inline int cant_mount(struct dentry *dentry)
+{
+ return (dentry->d_flags & DCACHE_CANT_MOUNT);
+}
+
+static inline void dont_mount(struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_CANT_MOUNT;
+ spin_unlock(&dentry->d_lock);
+}
+
static inline struct dentry *dget_parent(struct dentry *dentry)
{
struct dentry *ret;