On Sun, Dec 31, 2017 at 11:49 AM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> For a merge dir that was copied up before v4.12 or that was hand crafted
> offline (e.g. mkdir {upper/lower}/dir), upper dir does not contain the
> 'trusted.overlay.origin' xattr. In that case, stat(2) on the merge dir
> returns the lower dir st_ino, but getdents(2) returns the upper dir d_ino.
>
> After this change, on merge dir lookup, missing origin xattr on upper
> dir will be fixed and 'impure' xattr will be fixed on parent of the legacy
> merge dir.
>
> Suggested-by: zhangyi (F) <yi.zhang@xxxxxxxxxx>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
>
> Zhangyi,
>
> Please review/test this patch.
> I ended up applying it at the bottom of verify_dir [1] series,
> so it could be merged to v4.15 and/or easily backported to v4.14
> (where consistent d_ino was merged) if Miklos thinks this is an important
> use case to fix.
>
> Thanks,
> Amir.
>
> [1] https://github.com/amir73il/linux/commits/ovl-verify-dir
>
> fs/overlayfs/namei.c | 36 +++++++++++++++++++++++++++++++-----
> fs/overlayfs/overlayfs.h | 2 +-
> fs/overlayfs/super.c | 5 +++--
> 3 files changed, 35 insertions(+), 8 deletions(-)
>
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index 9cf15463754c..bd7375c05f7d 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -343,13 +343,13 @@ static int ovl_verify_origin_fh(struct dentry *dentry, const struct ovl_fh *fh)
> /*
> * Verify that an inode matches the origin file handle stored in upper inode.
> *
> - * If @set is true and there is no stored file handle, encode and store origin
> - * file handle in OVL_XATTR_ORIGIN.
> + * If @set is non-null and there is no stored file handle, set *@set to true
> + * and try to encode and store origin file handle in OVL_XATTR_ORIGIN.
> *
> - * Return 0 on match, -ESTALE on mismatch, < 0 on error.
> + * Return 0 on match or successful set, -ESTALE on mismatch, < 0 on error.
> */
> int ovl_verify_origin(struct dentry *dentry, struct dentry *origin,
> - bool is_upper, bool set)
> + bool is_upper, bool *set)
> {
> struct inode *inode;
> struct ovl_fh *fh;
> @@ -361,8 +361,13 @@ int ovl_verify_origin(struct dentry *dentry, struct dentry *origin,
> goto fail;
>
> err = ovl_verify_origin_fh(dentry, fh);
> - if (set && err == -ENODATA)
> + if (set && err == -ENODATA) {
> + *set = true;
> err = ovl_do_setxattr(dentry, OVL_XATTR_ORIGIN, fh, fh->len, 0);
> + if (err)
> + goto fail;
> + }
> +
> if (err)
> goto fail;
>
> @@ -674,6 +679,27 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> if (!this)
> continue;
>
> + /*
> + * If no origin fh is stored in upper of a merge dir, store fh
> + * of upper most lower dir and set upper parent "impure".
> + */
> + if (upperdentry && !ctr) {
> + bool set = false;
> +
> + err = ovl_verify_origin(upperdentry, this, false, &set);
> + if (set && !err) {
> + err = ovl_set_impure(dentry->d_parent,
> + upperdentry->d_parent);
> + }
Oh oh! this ovl_set_impure() is missing mnt_want_write(), but so do:
- set origin xattr in ovl_verify_origin()
- set opaque in ovl_make_workdir()
Will have to fix those too.
Amir.
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