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Merge branch 'work.sane_pwd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

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Pull misc vfs updates from Al Viro:
 "Making sure that something like a referral point won't end up as pwd
  or root.

  The main part is the last commit (fixing mntns_install()); that one
  fixes a hard-to-hit race. The fchdir() commit is making fchdir(2) a
  bit more robust - it should be impossible to get opened files (even
  O_PATH ones) for referral points in the first place, so the existing
  checks are OK, but checking the same thing as in chdir(2) is just as
  cheap.

  The path_init() commit removes a redundant check that shouldn't have
  been there in the first place"

* 'work.sane_pwd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  make sure that mntns_install() doesn't end up with referral for root
  path_init(): don't bother with checking MAY_EXEC for LOOKUP_ROOT
  make sure that fchdir() won't accept referral points, etc.
This commit is contained in:
Linus Torvalds 2017-05-12 11:39:59 -07:00
commit 050453295f
4 changed files with 55 additions and 21 deletions
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18
fs/namespace.c
View file

@ -3462,8 +3462,9 @@ 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) ||
@ -3474,15 +3475,18 @@ 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);