4.19-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro viro@zeniv.linux.org.uk
commit 399504e21a10be16dd1408ba0147367d9d82a10c upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/kernfs/mount.c | 8 ++++++-- kernel/cgroup/cgroup.c | 9 ++++++--- 2 files changed, 12 insertions(+), 5 deletions(-)
--- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -196,8 +196,10 @@ struct dentry *kernfs_node_dentry(struct 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 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); --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1998,7 +1998,7 @@ struct dentry *cgroup_do_mount(struct fi 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);
@@ -2008,6 +2008,7 @@ struct dentry *cgroup_do_mount(struct fi */ 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); @@ -2018,12 +2019,14 @@ struct dentry *cgroup_do_mount(struct fi 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;