On Wed, Nov 29, 2017 at 01:06:35PM +1100, NeilBrown wrote:

Subject: [PATCH] NFS: revalidate "." etc correctly on "open".

commit b688741cb06695312f18b730653d6611e1bad28d upstream.

For correct close-to-open semantics, NFS must validate the change attribute of a directory (or file) on open.

Since commit ecf3d1f1aa74 ("vfs: kill FS_REVAL_DOT by adding a d_weak_revalidate dentry op"), open() of "." or a path ending ".." is not revalidated reliably (except when that direct is a mount point).

Prior to that commit, "." was revalidated using nfs_lookup_revalidate() which checks the LOOKUP_OPEN flag and forces revalidation if the flag is set. Since that commit, nfs_weak_revalidate() is used for NFSv3 (which ignores the flags) and nothing is used for NFSv4.

This is fixed by using nfs_lookup_verify_inode() in nfs_weak_revalidate(). This does the revalidation exactly when needed. Also, add a definition of .d_weak_revalidate for NFSv4.

The incorrect behavior is easily demonstrated by running "echo *" in some non-mountpoint NFS directory while watching network traffic. Without this patch, "echo *" sometimes doesn't produce any traffic. With the patch it always does.

Fixes: ecf3d1f1aa74 ("vfs: kill FS_REVAL_DOT by adding a d_weak_revalidate dentry op") cc: stable@vger.kernel.org (3.9+) Signed-off-by: NeilBrown neilb@suse.com Signed-off-by: Anna Schumaker Anna.Schumaker@Netapp.com

---

fs/nfs/dir.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

This version applies to 3.18.y 4.4.y and 4.9.y

Thanks for the backport, now applied.

greg k-h