From b5891cfab08fe3144a616e8e734df7749fb3b7d0 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Sun, 31 Jan 2016 16:22:16 +0300 Subject: [PATCH 1/4] ovl: fix working on distributed fs as lower layer This adds missing .d_select_inode into alternative dentry_operations. Signed-off-by: Konstantin Khlebnikov Fixes: 7c03b5d45b8e ("ovl: allow distributed fs as lower layer") Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay") Reviewed-by: Nikolay Borisov Tested-by: Nikolay Borisov Signed-off-by: Miklos Szeredi Cc: # 4.2+ --- fs/overlayfs/super.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 8d826bd56b26..588a4b51ab0c 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -341,6 +341,7 @@ static const struct dentry_operations ovl_dentry_operations = { static const struct dentry_operations ovl_reval_dentry_operations = { .d_release = ovl_dentry_release, + .d_select_inode = ovl_d_select_inode, .d_revalidate = ovl_dentry_revalidate, .d_weak_revalidate = ovl_dentry_weak_revalidate, }; From ce9113bbcbf45a57c082d6603b9a9f342be3ef74 Mon Sep 17 00:00:00 2001 From: Rui Wang Date: Fri, 8 Jan 2016 23:09:59 +0800 Subject: [PATCH 2/4] ovl: fix getcwd() failure after unsuccessful rmdir ovl_remove_upper() should do d_drop() only after it successfully removes the dir, otherwise a subsequent getcwd() system call will fail, breaking userspace programs. This is to fix: https://bugzilla.kernel.org/show_bug.cgi?id=110491 Signed-off-by: Rui Wang Reviewed-by: Konstantin Khlebnikov Signed-off-by: Miklos Szeredi Cc: --- fs/overlayfs/dir.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index ed95272d57a6..795ab65ccdf5 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -618,7 +618,8 @@ static int ovl_remove_upper(struct dentry *dentry, bool is_dir) * sole user of this dentry. Too tricky... Just unhash for * now. */ - d_drop(dentry); + if (!err) + d_drop(dentry); inode_unlock(dir); return err; From 45d11738969633ec07ca35d75d486bf2d8918df6 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Sun, 31 Jan 2016 16:17:53 +0300 Subject: [PATCH 3/4] ovl: ignore lower entries when checking purity of non-directory entries After rename file dentry still holds reference to lower dentry from previous location. This doesn't matter for data access because data comes from upper dentry. But this stale lower dentry taints dentry at new location and turns it into non-pure upper. Such file leaves visible whiteout entry after remove in directory which shouldn't have whiteouts at all. Overlayfs already tracks pureness of file location in oe->opaque. This patch just uses that for detecting actual path type. Comment from Vivek Goyal's patch: Here are the details of the problem. Do following. $ mkdir upper lower work merged upper/dir/ $ touch lower/test $ sudo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir= work merged $ mv merged/test merged/dir/ $ rm merged/dir/test $ ls -l merged/dir/ /usr/bin/ls: cannot access merged/dir/test: No such file or directory total 0 c????????? ? ? ? ? ? test Basic problem seems to be that once a file has been unlinked, a whiteout has been left behind which was not needed and hence it becomes visible. Whiteout is visible because parent dir is of not type MERGE, hence od->is_real is set during ovl_dir_open(). And that means ovl_iterate() passes on iterate handling directly to underlying fs. Underlying fs does not know/filter whiteouts so it becomes visible to user. Why did we leave a whiteout to begin with when we should not have. ovl_do_remove() checks for OVL_TYPE_PURE_UPPER() and does not leave whiteout if file is pure upper. In this case file is not found to be pure upper hence whiteout is left. So why file was not PURE_UPPER in this case? I think because dentry is still carrying some leftover state which was valid before rename. For example, od->numlower was set to 1 as it was a lower file. After rename, this state is not valid anymore as there is no such file in lower. Signed-off-by: Konstantin Khlebnikov Reported-by: Viktor Stanchev Suggested-by: Vivek Goyal Link: https://bugzilla.kernel.org/show_bug.cgi?id=109611 Acked-by: Vivek Goyal Signed-off-by: Miklos Szeredi Cc: --- fs/overlayfs/dir.c | 7 +++++++ fs/overlayfs/super.c | 12 +++++++----- 2 files changed, 14 insertions(+), 5 deletions(-) diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index 795ab65ccdf5..52f6de5d40a9 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -904,6 +904,13 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old, if (!overwrite && new_is_dir && !old_opaque && new_opaque) ovl_remove_opaque(newdentry); + /* + * Old dentry now lives in different location. Dentries in + * lowerstack are stale. We cannot drop them here because + * access to them is lockless. This could be only pure upper + * or opaque directory - numlower is zero. Or upper non-dir + * entry - its pureness is tracked by flag opaque. + */ if (old_opaque != new_opaque) { ovl_dentry_set_opaque(old, new_opaque); if (!overwrite) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 588a4b51ab0c..619ad4b016d2 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -76,12 +76,14 @@ enum ovl_path_type ovl_path_type(struct dentry *dentry) if (oe->__upperdentry) { type = __OVL_PATH_UPPER; - if (oe->numlower) { - if (S_ISDIR(dentry->d_inode->i_mode)) - type |= __OVL_PATH_MERGE; - } else if (!oe->opaque) { + /* + * Non-dir dentry can hold lower dentry from previous + * location. Its purity depends only on opaque flag. + */ + if (oe->numlower && S_ISDIR(dentry->d_inode->i_mode)) + type |= __OVL_PATH_MERGE; + else if (!oe->opaque) type |= __OVL_PATH_PURE; - } } else { if (oe->numlower > 1) type |= __OVL_PATH_MERGE; From b81de061fa59f17d2730aabb1b84419ef3913810 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Sun, 31 Jan 2016 16:21:29 +0300 Subject: [PATCH 4/4] ovl: copy new uid/gid into overlayfs runtime inode Overlayfs must update uid/gid after chown, otherwise functions like inode_owner_or_capable() will check user against stale uid. Catched by xfstests generic/087, it chowns file and calls utimes. Signed-off-by: Konstantin Khlebnikov Signed-off-by: Miklos Szeredi Cc: --- fs/overlayfs/inode.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 49e204560655..a4ff5d0d7db9 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -65,6 +65,8 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr) inode_lock(upperdentry->d_inode); err = notify_change(upperdentry, attr, NULL); + if (!err) + ovl_copyattr(upperdentry->d_inode, dentry->d_inode); inode_unlock(upperdentry->d_inode); } ovl_drop_write(dentry);