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| author | Louis Rilling <louis.rilling@kerlabs.com> | 2008-06-23 14:16:17 +0200 |
|---|---|---|
| committer | Mark Fasheh <mfasheh@suse.com> | 2008-07-31 16:21:12 -0700 |
| commit | 4768e9b18dc63719209c68920d4ae52dc49b6161 (patch) | |
| tree | ee9e805c405ea6a6cdf44ba30fd66047bc522b1b /fs/configfs | |
| parent | dacdd0e04768da1fd2b24a6ee274c582b40d0c5b (diff) | |
| download | lwn-4768e9b18dc63719209c68920d4ae52dc49b6161.tar.gz lwn-4768e9b18dc63719209c68920d4ae52dc49b6161.zip | |
[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>
Diffstat (limited to 'fs/configfs')
| -rw-r--r-- | fs/configfs/dir.c | 14 | ||||
| -rw-r--r-- | fs/configfs/symlink.c | 6 |
2 files changed, 13 insertions, 7 deletions
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 2495f23e33f4..cb5ea44846af 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -370,6 +370,9 @@ static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex 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 @@ static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex *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 @@ static void configfs_detach_rollback(struct dentry *dentry) 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 0004d18c40ac..c12801a12c34 100644 --- a/fs/configfs/symlink.c +++ b/fs/configfs/symlink.c @@ -78,6 +78,12 @@ static int create_link(struct config_item *parent_item, 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, |