On Mon, 2018-05-28 at 11:59 +0200, Greg Kroah-Hartman wrote:
4.4-stable review patch. If anyone has any objections, please let me know.
From: Al Viro viro@zeniv.linux.org.uk
commit 1e2e547a93a00ebc21582c06ca3c6cfea2a309ee upstream.
For anything NFS-exported we do _not_ want to unlock new inode before it has grown an alias; original set of fixes got the ordering right, but missed the nasty complication in case of lockdep being enabled - unlock_new_inode() does lockdep_annotate_inode_mutex_key(inode) which can only be done before anyone gets a chance to touch ->i_mutex. Unfortunately, flipping the order and doing unlock_new_inode() before d_instantiate() opens a window when mkdir can race with open-by-fhandle on a guessed fhandle, leading to multiple aliases for a directory inode and all the breakage that follows from that.
Correct solution: a new primitive (d_instantiate_new()) combining these two in the right order - lockdep annotate, then d_instantiate(), then the rest of unlock_new_inode(). All combinations of d_instantiate() with unlock_new_inode() should be converted to that.
[...]
I think you missed xfs, which has a wrapper around unlock_new_inode() called xfs_finish_inode_setup(). It looks like xfs_generic_create() and xfs_vn_symlink() still need this conversion.
Ben.