From 9409e22acdfc9153f88d9b1ed2bd2a5b34d2d3ca Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 11 May 2016 01:16:37 +0200 Subject: vfs: rename: check backing inode being equal If a file is renamed to a hardlink of itself POSIX specifies that rename(2) should do nothing and return success. This condition is checked in vfs_rename(). However it won't detect hard links on overlayfs where these are given separate inodes on the overlayfs layer. Overlayfs itself detects this condition and returns success without doing anything, but then vfs_rename() will proceed as if this was a successful rename (detach_mounts(), d_move()). The correct thing to do is to detect this condition before even calling into overlayfs. This patch does this by calling vfs_select_inode() to get the underlying inodes. Signed-off-by: Miklos Szeredi Cc: # v4.2+ --- fs/namei.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 1d9ca2d5dff6..3ef87d673bbe 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -4213,7 +4213,11 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, bool new_is_dir = false; unsigned max_links = new_dir->i_sb->s_max_links; - if (source == target) + /* + * Check source == target. + * On overlayfs need to look at underlying inodes. + */ + if (vfs_select_inode(old_dentry, 0) == vfs_select_inode(new_dentry, 0)) return 0; error = may_delete(old_dir, old_dentry, is_dir); -- cgit v1.2.3 From 3c9fe8cdff1b889a059a30d22f130372f2b3885f Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 11 May 2016 01:16:37 +0200 Subject: vfs: add lookup_hash() helper Overlayfs needs lookup without inode_permission() and already has the name hash (in form of dentry->d_name on overlayfs dentry). It also doesn't support filesystems with d_op->d_hash() so basically it only needs the actual hashed lookup from lookup_one_len_unlocked() So add a new helper that does unlocked lookup of a hashed name. Signed-off-by: Miklos Szeredi --- fs/namei.c | 33 ++++++++++++++++++++++++++++----- include/linux/namei.h | 2 ++ 2 files changed, 30 insertions(+), 5 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 3ef87d673bbe..1a1ea79a7ba0 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2266,6 +2266,33 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, } EXPORT_SYMBOL(vfs_path_lookup); +/** + * lookup_hash - lookup single pathname component on already hashed name + * @name: name and hash to lookup + * @base: base directory to lookup from + * + * The name must have been verified and hashed (see lookup_one_len()). Using + * this after just full_name_hash() is unsafe. + * + * This function also doesn't check for search permission on base directory. + * + * Use lookup_one_len_unlocked() instead, unless you really know what you are + * doing. + * + * Do not hold i_mutex; this helper takes i_mutex if necessary. + */ +struct dentry *lookup_hash(const struct qstr *name, struct dentry *base) +{ + struct dentry *ret; + + ret = lookup_dcache(name, base, 0); + if (!ret) + ret = lookup_slow(name, base, 0); + + return ret; +} +EXPORT_SYMBOL(lookup_hash); + /** * lookup_one_len - filesystem helper to lookup single pathname component * @name: pathname component to lookup @@ -2337,7 +2364,6 @@ struct dentry *lookup_one_len_unlocked(const char *name, struct qstr this; unsigned int c; int err; - struct dentry *ret; this.name = name; this.len = len; @@ -2369,10 +2395,7 @@ struct dentry *lookup_one_len_unlocked(const char *name, if (err) return ERR_PTR(err); - ret = lookup_dcache(&this, base, 0); - if (!ret) - ret = lookup_slow(&this, base, 0); - return ret; + return lookup_hash(&this, base); } EXPORT_SYMBOL(lookup_one_len_unlocked); diff --git a/include/linux/namei.h b/include/linux/namei.h index 77d01700daf7..ec5ec2818a28 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -79,6 +79,8 @@ extern int kern_path_mountpoint(int, const char *, struct path *, unsigned int); extern struct dentry *lookup_one_len(const char *, struct dentry *, int); extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int); +struct qstr; +extern struct dentry *lookup_hash(const struct qstr *, struct dentry *); extern int follow_down_one(struct path *); extern int follow_down(struct path *); -- cgit v1.2.3