On 2019-11-16, Al Viro <v...@zeniv.linux.org.uk> wrote: > On Sat, Nov 16, 2019 at 11:27:56AM +1100, Aleksa Sarai wrote: > > > @@ -1383,6 +1398,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) > > return -ECHILD; > > if (&mparent->mnt == nd->path.mnt) > > break; > > + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) > > + return -EXDEV; > > /* we know that mountpoint was pinned */ > > nd->path.dentry = mountpoint; > > nd->path.mnt = &mparent->mnt; > > @@ -1397,6 +1414,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) > > return -ECHILD; > > if (!mounted) > > break; > > + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) > > + return -EXDEV; > > nd->path.mnt = &mounted->mnt; > > nd->path.dentry = mounted->mnt.mnt_root; > > inode = nd->path.dentry->d_inode; > > I really don't think we should return hard errors from that function. > Let the caller redo it in refwalk mode.
I suspected as much, though my reason for not changing it was that the mount_lock check should ensure that the cached status of whether ".." is a mountpoint crossing is correct. But I guess this is more about being safe than sorry, rather than an actual bug? > It's not the fast path, especially for this kind of errors. Matter of > fact, I'm not sure about -ENOENT returned in another failure case > there - it's probably OK, but again, -ECHILD would be just as good. I can switch the -ENOENT too if you like. -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH <https://www.cyphar.com/>
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