3.5.7.19 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov <oleg@xxxxxxxxxx> commit 776164c1faac4966ab14418bb0922e1820da1d19 upstream. debugfs_remove_recursive() is wrong, 1. it wrongly assumes that !list_empty(d_subdirs) means that this dir should be removed. This is not that bad by itself, but: 2. if d_subdirs does not becomes empty after __debugfs_remove() it gives up and silently fails, it doesn't even try to remove other entries. However ->d_subdirs can be non-empty because it still has the already deleted !debugfs_positive() entries. 3. simple_release_fs() is called even if __debugfs_remove() fails. Suppose we have dir1/ dir2/ file2 file1 and someone opens dir1/dir2/file2. Now, debugfs_remove_recursive(dir1/dir2) succeeds, and dir1/dir2 goes away. But debugfs_remove_recursive(dir1) silently fails and doesn't remove this directory. Because it tries to delete (the already deleted) dir1/dir2/file2 again and then fails due to "Avoid infinite loop" logic. Test-case: #!/bin/sh cd /sys/kernel/debug/tracing echo 'p:probe/sigprocmask sigprocmask' >> kprobe_events sleep 1000 < events/probe/sigprocmask/id & echo -n >| kprobe_events [ -d events/probe ] && echo "ERR!! failed to rm probe" And after that it is not possible to create another probe entry. With this patch debugfs_remove_recursive() skips !debugfs_positive() files although this is not strictly needed. The most important change is that it does not try to make ->d_subdirs empty, it simply scans the whole list(s) recursively and removes as much as possible. Link: http://lkml.kernel.org/r/20130726151256.GC19472@xxxxxxxxxx Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx> --- fs/debugfs/inode.c | 69 +++++++++++++++++------------------------------------- 1 file changed, 22 insertions(+), 47 deletions(-) diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index b80bc84..9dc6e76 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -527,8 +527,7 @@ EXPORT_SYMBOL_GPL(debugfs_remove); */ void debugfs_remove_recursive(struct dentry *dentry) { - struct dentry *child; - struct dentry *parent; + struct dentry *child, *next, *parent; if (!dentry) return; @@ -538,61 +537,37 @@ void debugfs_remove_recursive(struct dentry *dentry) return; parent = dentry; + down: mutex_lock(&parent->d_inode->i_mutex); + list_for_each_entry_safe(child, next, &parent->d_subdirs, d_u.d_child) { + if (!debugfs_positive(child)) + continue; - while (1) { - /* - * When all dentries under "parent" has been removed, - * walk up the tree until we reach our starting point. - */ - if (list_empty(&parent->d_subdirs)) { - mutex_unlock(&parent->d_inode->i_mutex); - if (parent == dentry) - break; - parent = parent->d_parent; - mutex_lock(&parent->d_inode->i_mutex); - } - child = list_entry(parent->d_subdirs.next, struct dentry, - d_u.d_child); - next_sibling: - - /* - * If "child" isn't empty, walk down the tree and - * remove all its descendants first. - */ + /* perhaps simple_empty(child) makes more sense */ if (!list_empty(&child->d_subdirs)) { mutex_unlock(&parent->d_inode->i_mutex); parent = child; - mutex_lock(&parent->d_inode->i_mutex); - continue; + goto down; } - __debugfs_remove(child, parent); - if (parent->d_subdirs.next == &child->d_u.d_child) { - /* - * Try the next sibling. - */ - if (child->d_u.d_child.next != &parent->d_subdirs) { - child = list_entry(child->d_u.d_child.next, - struct dentry, - d_u.d_child); - goto next_sibling; - } - - /* - * Avoid infinite loop if we fail to remove - * one dentry. - */ - mutex_unlock(&parent->d_inode->i_mutex); - break; - } - simple_release_fs(&debugfs_mount, &debugfs_mount_count); + up: + if (!__debugfs_remove(child, parent)) + simple_release_fs(&debugfs_mount, &debugfs_mount_count); } - parent = dentry->d_parent; + mutex_unlock(&parent->d_inode->i_mutex); + child = parent; + parent = parent->d_parent; mutex_lock(&parent->d_inode->i_mutex); - __debugfs_remove(dentry, parent); + + if (child != dentry) { + next = list_entry(child->d_u.d_child.next, struct dentry, + d_u.d_child); + goto up; + } + + if (!__debugfs_remove(child, parent)) + simple_release_fs(&debugfs_mount, &debugfs_mount_count); mutex_unlock(&parent->d_inode->i_mutex); - simple_release_fs(&debugfs_mount, &debugfs_mount_count); } EXPORT_SYMBOL_GPL(debugfs_remove_recursive); -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html