On Tue, Apr 08, 2014 at 05:21:32PM -0700, Eric W. Biederman wrote: > This set of changes has been reviewed and been sitting idle for the last > 6 weeks. In that time the vfs has slightly shifted under me the new > version of rename and the mount hash list becoming a hlist. None of > those changes has caused changed the code in ways to invalidate these > changes, but small conflicts do result and I have attached my conflict > resolution at the end of this email in case it helps. > > To recap these changes allow a file or a directory that is a mount point > in one mount namespace to be unlinked/rmdired elsewhere where it is not > a mount point (either a remote filesystem or another mount namespace). > As has been agreed during review semantics when only a single mount > namespace exists remain unchanged. > > This removes a long standing need to lie to the vfs when a mount point > has been removed behind it's back. This also removes a DOS attack where > an unprivileged user could prevent root from renaming or deleting files > and directories by using them as mountpoints in another mount namespace. > > This change also fixes a few cases where because we were not lying to > the vfs we could leak mount points. > > When renaming or unlinking directory entries that are not mountpoints > no additional locks are taken so no performance differences can result, > and my benchmark reflected that. It also means that d_invalidate() now might trigger fs shutdown. Which has bloody huge stack footprint, for obvious reasons. And d_invalidate() can be called with pretty deep stack - walk into wrong dentry while resolving a deeply nested symlink and there you go... -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
