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Subject[PATCH 02/73] VFS: Make clone_mnt()/copy_tree()/collect_mounts() return errors [ver #2]
Date
copy_tree() can theoretically fail in a case other than ENOMEM, but always
returns NULL which is interpreted by callers as -ENOMEM. Change it to return
an explicit error.

Also change clone_mnt() for consistency and because union mounts will add new
error cases.

Thanks to Andreas Gruenbacher <agruen@suse.de> for a bug fix.

Original-author: Valerie Aurora <vaurora@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Valerie Aurora <valerie.aurora@gmail.com>
Cc: Andreas Gruenbacher <agruen@suse.de>
---

fs/namespace.c | 116 +++++++++++++++++++++++++++------------------------
fs/pnode.c | 5 +-
kernel/audit_tree.c | 10 ++--
3 files changed, 70 insertions(+), 61 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index e608199..baedd0b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -725,56 +725,60 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
int flag)
{
struct super_block *sb = old->mnt.mnt_sb;
- struct mount *mnt = alloc_vfsmnt(old->mnt_devname);
+ struct mount *mnt;
+ int err;

- if (mnt) {
- if (flag & (CL_SLAVE | CL_PRIVATE))
- mnt->mnt_group_id = 0; /* not a peer of original */
- else
- mnt->mnt_group_id = old->mnt_group_id;
-
- if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
- int err = mnt_alloc_group_id(mnt);
- if (err)
- goto out_free;
- }
+ mnt = alloc_vfsmnt(old->mnt_devname);
+ if (!mnt)
+ return ERR_PTR(-ENOMEM);

- mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
- atomic_inc(&sb->s_active);
- mnt->mnt.mnt_sb = sb;
- mnt->mnt.mnt_root = dget(root);
- mnt->mnt_mountpoint = mnt->mnt.mnt_root;
- mnt->mnt_parent = mnt;
- br_write_lock(vfsmount_lock);
- list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
- br_write_unlock(vfsmount_lock);
+ if (flag & (CL_SLAVE | CL_PRIVATE))
+ mnt->mnt_group_id = 0; /* not a peer of original */
+ else
+ mnt->mnt_group_id = old->mnt_group_id;

- if (flag & CL_SLAVE) {
- list_add(&mnt->mnt_slave, &old->mnt_slave_list);
- mnt->mnt_master = old;
- CLEAR_MNT_SHARED(mnt);
- } else if (!(flag & CL_PRIVATE)) {
- if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
- list_add(&mnt->mnt_share, &old->mnt_share);
- if (IS_MNT_SLAVE(old))
- list_add(&mnt->mnt_slave, &old->mnt_slave);
- mnt->mnt_master = old->mnt_master;
- }
- if (flag & CL_MAKE_SHARED)
- set_mnt_shared(mnt);
-
- /* stick the duplicate mount on the same expiry list
- * as the original if that was on one */
- if (flag & CL_EXPIRE) {
- if (!list_empty(&old->mnt_expire))
- list_add(&mnt->mnt_expire, &old->mnt_expire);
- }
+ if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
+ err = mnt_alloc_group_id(mnt);
+ if (err)
+ goto out_free;
}
+
+ mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
+ atomic_inc(&sb->s_active);
+ mnt->mnt.mnt_sb = sb;
+ mnt->mnt.mnt_root = dget(root);
+ mnt->mnt_mountpoint = mnt->mnt.mnt_root;
+ mnt->mnt_parent = mnt;
+ br_write_lock(vfsmount_lock);
+ list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
+ br_write_unlock(vfsmount_lock);
+
+ if (flag & CL_SLAVE) {
+ list_add(&mnt->mnt_slave, &old->mnt_slave_list);
+ mnt->mnt_master = old;
+ CLEAR_MNT_SHARED(mnt);
+ } else if (!(flag & CL_PRIVATE)) {
+ if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
+ list_add(&mnt->mnt_share, &old->mnt_share);
+ if (IS_MNT_SLAVE(old))
+ list_add(&mnt->mnt_slave, &old->mnt_slave);
+ mnt->mnt_master = old->mnt_master;
+ }
+ if (flag & CL_MAKE_SHARED)
+ set_mnt_shared(mnt);
+
+ /* stick the duplicate mount on the same expiry list as the
+ * original if that was on one */
+ if (flag & CL_EXPIRE) {
+ if (!list_empty(&old->mnt_expire))
+ list_add(&mnt->mnt_expire, &old->mnt_expire);
+ }
+
return mnt;

out_free:
free_vfsmnt(mnt);
- return NULL;
+ return ERR_PTR(err);
}

static inline void mntfree(struct mount *mnt)
@@ -1258,11 +1262,12 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
struct path path;

if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
- return NULL;
+ return ERR_PTR(-EINVAL);

res = q = clone_mnt(mnt, dentry, flag);
- if (!q)
- goto Enomem;
+ if (IS_ERR(q))
+ return q;
+
q->mnt_mountpoint = mnt->mnt_mountpoint;

p = mnt;
@@ -1284,8 +1289,8 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
path.mnt = &q->mnt;
path.dentry = p->mnt_mountpoint;
q = clone_mnt(p, p->mnt.mnt_root, flag);
- if (!q)
- goto Enomem;
+ if (IS_ERR(q))
+ goto out;
br_write_lock(vfsmount_lock);
list_add_tail(&q->mnt_list, &res->mnt_list);
attach_mnt(q, &path);
@@ -1293,7 +1298,7 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
}
}
return res;
-Enomem:
+out:
if (res) {
LIST_HEAD(umount_list);
br_write_lock(vfsmount_lock);
@@ -1301,9 +1306,11 @@ Enomem:
br_write_unlock(vfsmount_lock);
release_mounts(&umount_list);
}
- return NULL;
+ return q;
}

+/* Caller should check returned pointer for errors */
+
struct vfsmount *collect_mounts(struct path *path)
{
struct mount *tree;
@@ -1606,14 +1613,15 @@ static int do_loopback(struct path *path, char *old_name,
if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old))
goto out2;

- err = -ENOMEM;
if (recurse)
mnt = copy_tree(old, old_path.dentry, 0);
else
mnt = clone_mnt(old, old_path.dentry, 0);

- if (!mnt)
- goto out2;
+ if (IS_ERR(mnt)) {
+ err = PTR_ERR(mnt);
+ goto out;
+ }

err = graft_tree(mnt, path);
if (err) {
@@ -2244,10 +2252,10 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
down_write(&namespace_sem);
/* First pass: copy the tree topology */
new = copy_tree(old, old->mnt.mnt_root, CL_COPY_ALL | CL_EXPIRE);
- if (!new) {
+ if (IS_ERR(new)) {
up_write(&namespace_sem);
kfree(new_ns);
- return ERR_PTR(-ENOMEM);
+ return ERR_CAST(new);
}
new_ns->root = new;
br_write_lock(vfsmount_lock);
diff --git a/fs/pnode.c b/fs/pnode.c
index ab5fa9e..b79d27c 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -237,8 +237,9 @@ int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,

source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);

- if (!(child = copy_tree(source, source->mnt.mnt_root, type))) {
- ret = -ENOMEM;
+ child = copy_tree(source, source->mnt.mnt_root, type);
+ if (IS_ERR(child)) {
+ ret = PTR_ERR(child);
list_splice(tree_list, tmp_list.prev);
goto out;
}
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 5bf0790..3a5ca58 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -595,7 +595,7 @@ void audit_trim_trees(void)

root_mnt = collect_mounts(&path);
path_put(&path);
- if (!root_mnt)
+ if (IS_ERR(root_mnt))
goto skip_it;

spin_lock(&hash_lock);
@@ -669,8 +669,8 @@ int audit_add_tree_rule(struct audit_krule *rule)
goto Err;
mnt = collect_mounts(&path);
path_put(&path);
- if (!mnt) {
- err = -ENOMEM;
+ if (IS_ERR(mnt)) {
+ err = PTR_ERR(mnt);
goto Err;
}

@@ -719,8 +719,8 @@ int audit_tag_tree(char *old, char *new)
return err;
tagged = collect_mounts(&path2);
path_put(&path2);
- if (!tagged)
- return -ENOMEM;
+ if (IS_ERR(tagged))
+ return PTR_ERR(tagged);

err = kern_path(old, 0, &path1);
if (err) {


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