On Thu, Oct 12, 2017 at 07:03:04PM +0300, Amir Goldstein wrote:
> Commit fbaf94ee3cd5 ("ovl: don't set origin on broken lower hardlink")
> attempt to avoid the condition of non-indexed upper inode with lower
> hardlink as origin. If this condition is found, lookup returns EIO.
>
> The protection of commit mentioned above does not cover the case of lower
> that is not a hardlink when it is copied up (with either index=off/on)
> and then lower is hardlinked while overlay is offline.
>
> Changes to lower layer while overlayfs is offline should not result in
> unexpected behavior, so a permanent EIO error after creating a link in
> lower layer should not be considered as correct behavior.
>
> This fix replaces EIO error with a warning in cases where upper has
> origin but no index is found, or index is found that does not match upper
> inode. In those cases, lookup will not fail and the returned overlay
> inode will be hashed by upper inode instead of by lower origin inode.
>
> Fixes: 359f392ca53e ("ovl: lookup index entry for copy up origin")
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.13
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
>
> Miklos,
>
> Following a discussion with Vivek about metacopy feature and the option
> of setting ORIGIN for non-indexed lower hardlinks on copy up, I came to
> a conclusion that the current EIO behavior is not quite tollerant to lower
> changes as one would hope and that it should be fixed in stable kernels.
>
> I've implemented an xfstest to test the EIO behavior has been fixed [1].
>
> Amir.
>
> [1] https://github.com/amir73il/xfstests/commits/overlayfs-devel
>
> fs/overlayfs/inode.c | 20 ++++++++++++++++----
> fs/overlayfs/namei.c | 22 ++++++++++++----------
> fs/overlayfs/overlayfs.h | 3 ++-
> 3 files changed, 30 insertions(+), 15 deletions(-)
>
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index a619addecafc..321511ed8c42 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -598,18 +598,30 @@ static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
> return true;
> }
>
> -struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry)
> +struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry,
> + struct dentry *index)
> {
> struct dentry *lowerdentry = ovl_dentry_lower(dentry);
> struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL;
> struct inode *inode;
> + /* Already indexed or could be indexed on copy up? */
> + bool indexed = (index || (ovl_indexdir(dentry->d_sb) && !upperdentry));
Hi Amir,
Looks like current code hashes inodes of lowerdentry even if nlink=1
(index=on, upperdentry=NULL). IIUC this will never be indexed.
So I am wondering why do we hash inodes of lower when nlink=1. When is it
used.
Vivek
> +
> + if (WARN_ON(upperdentry && indexed && !lowerdentry))
> + return ERR_PTR(-EIO);
>
> if (!realinode)
> realinode = d_inode(lowerdentry);
>
> - if (!S_ISDIR(realinode->i_mode) &&
> - (upperdentry || (lowerdentry && ovl_indexdir(dentry->d_sb)))) {
> - struct inode *key = d_inode(lowerdentry ?: upperdentry);
> + /*
> + * Copy up origin (lower) may exist for non-indexed upper, but we must
> + * not use lower as hash key in that case.
> + * Hash inodes that are or could be indexed by origin inode and
> + * non-indexed upper inodes that could be hard linked by upper inode.
> + */
> + if (!S_ISDIR(realinode->i_mode) && (upperdentry || indexed)) {
> + struct inode *key = d_inode(indexed ? lowerdentry :
> + upperdentry);
> unsigned int nlink;
>
> inode = iget5_locked(dentry->d_sb, (unsigned long) key,
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index 654bea1a5ac9..88ff1daeb3d7 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -517,17 +517,14 @@ static struct dentry *ovl_lookup_index(struct dentry *dentry,
> inode = d_inode(index);
> if (d_is_negative(index)) {
> if (upper && d_inode(origin)->i_nlink > 1) {
> - pr_warn_ratelimited("overlayfs: hard link with origin but no index (ino=%lu).\n",
> - d_inode(origin)->i_ino);
> - goto fail;
> + pr_warn_ratelimited("overlayfs: hard link with origin but no index (%pd2).\n",
> + upper);
> }
> -
> - dput(index);
> - index = NULL;
> + goto out_dput;
> } else if (upper && d_inode(upper) != inode) {
> - pr_warn_ratelimited("overlayfs: wrong index found (index=%pd2, ino=%lu, upper ino=%lu).\n",
> - index, inode->i_ino, d_inode(upper)->i_ino);
> - goto fail;
> + pr_warn_ratelimited("overlayfs: broken hard link - ignoring index (%pd2).\n",
> + upper);
> + goto out_dput;
> } else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) ||
> ((inode->i_mode ^ d_inode(origin)->i_mode) & S_IFMT)) {
> /*
> @@ -547,6 +544,11 @@ static struct dentry *ovl_lookup_index(struct dentry *dentry,
> kfree(name.name);
> return index;
>
> +out_dput:
> + dput(index);
> + index = NULL;
> + goto out;
> +
> fail:
> dput(index);
> index = ERR_PTR(-EIO);
> @@ -709,7 +711,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> upperdentry = dget(index);
>
> if (upperdentry || ctr) {
> - inode = ovl_get_inode(dentry, upperdentry);
> + inode = ovl_get_inode(dentry, upperdentry, index);
> err = PTR_ERR(inode);
> if (IS_ERR(inode))
> goto out_free_oe;
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index c706a6f99928..d9a0edd4e57e 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -286,7 +286,8 @@ int ovl_update_time(struct inode *inode, struct timespec *ts, int flags);
> bool ovl_is_private_xattr(const char *name);
>
> struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev);
> -struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry);
> +struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry,
> + struct dentry *index);
> static inline void ovl_copyattr(struct inode *from, struct inode *to)
> {
> to->i_uid = from->i_uid;
> --
> 2.7.4
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