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authorAl Viro <viro@zeniv.linux.org.uk>2017-04-16 00:31:22 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2017-04-21 21:05:36 +0300
commit4f757f3cbf54edef7b75c68d6d6d2f1a0ca08d2e (patch)
treeea39abd6e1941de602264b24ee18c82f12c01c04 /fs/namespace.c
parent93893862fb7ba704ec5a6872a294c9cc2b0d4ca3 (diff)
downloadlinux-4f757f3cbf54edef7b75c68d6d6d2f1a0ca08d2e.tar.xz
make sure that mntns_install() doesn't end up with referral for root
new flag: LOOKUP_DOWN. If the starting point is overmounted, cross into whatever's mounted on top, triggering referrals et.al. Use that instead of follow_down_one() loop in mntns_install(), handle errors properly. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r--fs/namespace.c18
1 files changed, 11 insertions, 7 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index cc1375eff88c..0886ef28bff6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3465,8 +3465,9 @@ static void mntns_put(struct ns_common *ns)
static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
{
struct fs_struct *fs = current->fs;
- struct mnt_namespace *mnt_ns = to_mnt_ns(ns);
+ struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
struct path root;
+ int err;
if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
!ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
@@ -3477,15 +3478,18 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
return -EINVAL;
get_mnt_ns(mnt_ns);
- put_mnt_ns(nsproxy->mnt_ns);
+ old_mnt_ns = nsproxy->mnt_ns;
nsproxy->mnt_ns = mnt_ns;
/* Find the root */
- root.mnt = &mnt_ns->root->mnt;
- root.dentry = mnt_ns->root->mnt.mnt_root;
- path_get(&root);
- while(d_mountpoint(root.dentry) && follow_down_one(&root))
- ;
+ err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
+ "/", LOOKUP_DOWN, &root);
+ if (err) {
+ /* revert to old namespace */
+ nsproxy->mnt_ns = old_mnt_ns;
+ put_mnt_ns(mnt_ns);
+ return err;
+ }
/* Update the pwd and root */
set_fs_pwd(fs, &root);