[PATCH 01/43] fix cgroup_do_mount() handling of failure exits
From: David Howells <dhowells@redhat.com>
Date: 2019-02-19 16:28:15
Also in:
linux-fsdevel
Subsystem:
control group (cgroup), filesystems (vfs and infrastructure), kernfs, the rest · Maintainers:
Tejun Heo, Johannes Weiner, Michal Koutný, Alexander Viro, Christian Brauner, Greg Kroah-Hartman, Linus Torvalds
From: Al Viro <viro@zeniv.linux.org.uk> same story as with last May fixes in sysfs (7b745a4e4051 "unfuck sysfs_mount()"); new_sb is left uninitialized in case of early errors in kernfs_mount_ns() and papering over it by treating any error from kernfs_mount_ns() as equivalent to !new_ns ends up conflating the cases when objects had never been transferred to a superblock with ones when that has happened and resulting new superblock had been dropped. Easily fixed (same way as in sysfs case). Additionally, there's a superblock leak on kernfs_node_dentry() failure *and* a dentry leak inside kernfs_node_dentry() itself - the latter on probably impossible errors, but the former not impossible to trigger (as the matter of fact, injecting allocation failures at that point *does* trigger it). Cc: stable@kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> --- fs/kernfs/mount.c | 8 ++++++-- kernel/cgroup/cgroup.c | 9 ++++++--- 2 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index fdf527b6d79c..d71c9405874a 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c@@ -196,8 +196,10 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn, return dentry; knparent = find_next_ancestor(kn, NULL); - if (WARN_ON(!knparent)) + if (WARN_ON(!knparent)) { + dput(dentry); return ERR_PTR(-EINVAL); + } do { struct dentry *dtmp;
@@ -206,8 +208,10 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn, if (kn == knparent) return dentry; kntmp = find_next_ancestor(kn, knparent); - if (WARN_ON(!kntmp)) + if (WARN_ON(!kntmp)) { + dput(dentry); return ERR_PTR(-EINVAL); + } dtmp = lookup_one_len_unlocked(kntmp->name, dentry, strlen(kntmp->name)); dput(dentry);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index f31bd61c9466..503bba3c4bae 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c@@ -2033,7 +2033,7 @@ struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags, struct cgroup_namespace *ns) { struct dentry *dentry; - bool new_sb; + bool new_sb = false; dentry = kernfs_mount(fs_type, flags, root->kf_root, magic, &new_sb);
@@ -2043,6 +2043,7 @@ struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags, */ if (!IS_ERR(dentry) && ns != &init_cgroup_ns) { struct dentry *nsdentry; + struct super_block *sb = dentry->d_sb; struct cgroup *cgrp; mutex_lock(&cgroup_mutex);
@@ -2053,12 +2054,14 @@ struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags, spin_unlock_irq(&css_set_lock); mutex_unlock(&cgroup_mutex); - nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb); + nsdentry = kernfs_node_dentry(cgrp->kn, sb); dput(dentry); + if (IS_ERR(nsdentry)) + deactivate_locked_super(sb); dentry = nsdentry; } - if (IS_ERR(dentry) || !new_sb) + if (!new_sb) cgroup_put(&root->cgrp); return dentry;