forked from Minki/linux
7e63c87fc2
In the past, overlayfs required that lower fs have non null uuid in order to support nfs export and decode copy up origin file handles. Commit9df085f3c9("ovl: relax requirement for non null uuid of lower fs") relaxed this requirement for nfs export support, as long as uuid (even if null) is unique among all lower fs. However, said commit unintentionally also relaxed the non null uuid requirement for decoding copy up origin file handles, regardless of the unique uuid requirement. Amend this mistake by disabling decoding of copy up origin file handle from lower fs with a conflicting uuid. We still encode copy up origin file handles from those fs, because file handles like those already exist in the wild and because they might provide useful information in the future. There is an unhandled corner case described by Miklos this way: - two filesystems, A and B, both have null uuid - upper layer is on A - lower layer 1 is also on A - lower layer 2 is on B In this case bad_uuid won't be set for B, because the check only involves the list of lower fs. Hence we'll try to decode a layer 2 origin on layer 1 and fail. We will deal with this corner case later. Reported-by: Colin Ian King <colin.king@canonical.com> Tested-by: Colin Ian King <colin.king@canonical.com> Link: https://lore.kernel.org/lkml/20191106234301.283006-1-colin.king@canonical.com/ Fixes:9df085f3c9("ovl: relax requirement for non null uuid ...") Cc: stable@vger.kernel.org # v4.20+ Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
122 lines
2.8 KiB
C
122 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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*
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* Copyright (C) 2011 Novell Inc.
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* Copyright (C) 2016 Red Hat, Inc.
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*/
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struct ovl_config {
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char *lowerdir;
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char *upperdir;
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char *workdir;
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bool default_permissions;
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bool redirect_dir;
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bool redirect_follow;
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const char *redirect_mode;
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bool index;
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bool nfs_export;
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int xino;
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bool metacopy;
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};
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struct ovl_sb {
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struct super_block *sb;
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dev_t pseudo_dev;
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/* Unusable (conflicting) uuid */
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bool bad_uuid;
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};
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struct ovl_layer {
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struct vfsmount *mnt;
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/* Trap in ovl inode cache */
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struct inode *trap;
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struct ovl_sb *fs;
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/* Index of this layer in fs root (upper idx == 0) */
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int idx;
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/* One fsid per unique underlying sb (upper fsid == 0) */
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int fsid;
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};
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struct ovl_path {
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struct ovl_layer *layer;
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struct dentry *dentry;
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};
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/* private information held for overlayfs's superblock */
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struct ovl_fs {
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struct vfsmount *upper_mnt;
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unsigned int numlower;
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/* Number of unique lower sb that differ from upper sb */
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unsigned int numlowerfs;
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struct ovl_layer *lower_layers;
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struct ovl_sb *lower_fs;
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/* workbasedir is the path at workdir= mount option */
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struct dentry *workbasedir;
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/* workdir is the 'work' directory under workbasedir */
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struct dentry *workdir;
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/* index directory listing overlay inodes by origin file handle */
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struct dentry *indexdir;
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long namelen;
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/* pathnames of lower and upper dirs, for show_options */
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struct ovl_config config;
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/* creds of process who forced instantiation of super block */
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const struct cred *creator_cred;
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bool tmpfile;
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bool noxattr;
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/* Did we take the inuse lock? */
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bool upperdir_locked;
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bool workdir_locked;
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/* Traps in ovl inode cache */
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struct inode *upperdir_trap;
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struct inode *workbasedir_trap;
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struct inode *workdir_trap;
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struct inode *indexdir_trap;
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/* Inode numbers in all layers do not use the high xino_bits */
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unsigned int xino_bits;
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};
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/* private information held for every overlayfs dentry */
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struct ovl_entry {
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union {
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struct {
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unsigned long flags;
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};
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struct rcu_head rcu;
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};
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unsigned numlower;
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struct ovl_path lowerstack[];
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};
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struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
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static inline struct ovl_entry *OVL_E(struct dentry *dentry)
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{
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return (struct ovl_entry *) dentry->d_fsdata;
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}
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struct ovl_inode {
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union {
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struct ovl_dir_cache *cache; /* directory */
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struct inode *lowerdata; /* regular file */
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};
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const char *redirect;
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u64 version;
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unsigned long flags;
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struct inode vfs_inode;
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struct dentry *__upperdentry;
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struct inode *lower;
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/* synchronize copy up and more */
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struct mutex lock;
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};
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static inline struct ovl_inode *OVL_I(struct inode *inode)
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{
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return container_of(inode, struct ovl_inode, vfs_inode);
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}
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static inline struct dentry *ovl_upperdentry_dereference(struct ovl_inode *oi)
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{
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return READ_ONCE(oi->__upperdentry);
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}
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