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separate copying and locking mount tree on cross-userns copies

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Rather than having propagate_mnt() check doing unprivileged copies,
lock them before commit_tree().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2019-01-30 13:15:45 -05:00
parent 6d7fbce7da
commit 3bd045cc9c
3 changed files with 38 additions and 29 deletions
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5
fs/pnode.c
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@ -214,7 +214,6 @@ static struct mount *next_group(struct mount *m, struct mount *origin)
}
/* all accesses are serialized by namespace_sem */
static struct user_namespace *user_ns;
static struct mount *last_dest, *first_source, *last_source, *dest_master;
static struct mountpoint *mp;
static struct hlist_head *list;
@ -260,9 +259,6 @@ static int propagate_one(struct mount *m)
type |= CL_MAKE_SHARED;
}
/* Notice when we are propagating across user namespaces */
if (m->mnt_ns->user_ns != user_ns)
type |= CL_UNPRIVILEGED;
child = copy_tree(last_source, last_source->mnt.mnt_root, type);
if (IS_ERR(child))
return PTR_ERR(child);
@ -303,7 +299,6 @@ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
* propagate_one(); everything is serialized by namespace_sem,
* so globals will do just fine.
*/
user_ns = current->nsproxy->mnt_ns->user_ns;
last_dest = dest_mnt;
first_source = source_mnt;
last_source = source_mnt;