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ovl: fix EIO from lookup of non-indexed upper

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Commit fbaf94ee3c ("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 success 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: 359f392ca5 ("ovl: lookup index entry for copy up origin")
Cc: <stable@vger.kernel.org> # v4.13
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Amir Goldstein
2017-10-12 19:03:04 +03:00
committed by Miklos Szeredi
parent 0ce5cdc9d7
commit 6eaf011144
3 changed files with 26 additions and 17 deletions
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20
fs/overlayfs/inode.c
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@@ -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));
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,