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@xxxxxxxxxxxxxxx (3.9+)
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>
> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
> ---
> 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