[PATCH] configfs: Fix symlink() to a removing item
The rule for configfs symlinks is that symlinks always point to valid
config_items, and prevent the target from being removed. However,
configfs_symlink() only checks that it can grab a reference on the target item,
without ensuring that it remains alive until the symlink is correctly attached.
This patch makes configfs_symlink() fail whenever the target is being removed,
using the CONFIGFS_USET_DROPPING flag set by configfs_detach_prep() and
protected by configfs_dirent_lock.
This patch introduces a similar (weird?) behavior as with mkdir failures making
rmdir fail: if symlink() races with rmdir() of the parent directory (or its
youngest user-created ancestor if parent is a default group) or rmdir() of the
target directory, and then fails in configfs_create(), this can make the racing
rmdir() fail despite the concerned directory having no user-created entry (resp.
no symlink pointing to it or one of its default groups) in the end.
This behavior is fixed in later patches.
Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 2495f23..cb5ea44 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -370,6 +370,9 @@
struct configfs_dirent *sd;
int ret;
+ /* Mark that we're trying to drop the group */
+ parent_sd->s_type |= CONFIGFS_USET_DROPPING;
+
ret = -EBUSY;
if (!list_empty(&parent_sd->s_links))
goto out;
@@ -385,8 +388,6 @@
*wait_mutex = &sd->s_dentry->d_inode->i_mutex;
return -EAGAIN;
}
- /* Mark that we're trying to drop the group */
- sd->s_type |= CONFIGFS_USET_DROPPING;
/*
* Yup, recursive. If there's a problem, blame
@@ -414,12 +415,11 @@
struct configfs_dirent *parent_sd = dentry->d_fsdata;
struct configfs_dirent *sd;
- list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
- if (sd->s_type & CONFIGFS_USET_DEFAULT) {
+ parent_sd->s_type &= ~CONFIGFS_USET_DROPPING;
+
+ list_for_each_entry(sd, &parent_sd->s_children, s_sibling)
+ if (sd->s_type & CONFIGFS_USET_DEFAULT)
configfs_detach_rollback(sd->s_dentry);
- sd->s_type &= ~CONFIGFS_USET_DROPPING;
- }
- }
}
static void detach_attrs(struct config_item * item)
diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c
index 0004d18..c12801a 100644
--- a/fs/configfs/symlink.c
+++ b/fs/configfs/symlink.c
@@ -78,6 +78,12 @@
if (sl) {
sl->sl_target = config_item_get(item);
spin_lock(&configfs_dirent_lock);
+ if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
+ spin_unlock(&configfs_dirent_lock);
+ config_item_put(item);
+ kfree(sl);
+ return -ENOENT;
+ }
list_add(&sl->sl_list, &target_sd->s_links);
spin_unlock(&configfs_dirent_lock);
ret = configfs_create_link(sl, parent_item->ci_dentry,
