forked from luck/tmp_suning_uos_patched
Allow O_PATH for symlinks
At that point we can't do almost nothing with them. They can be opened with O_PATH, we can manipulate such descriptors with dup(), etc. and we can see them in /proc/*/{fd,fdinfo}/*. We can't (and won't be able to) follow /proc/*/fd/* symlinks for those; there's simply not enough information for pathname resolution to go on from such point - to resolve a symlink we need to know which directory does it live in. We will be able to do useful things with them after the next commit, though - readlinkat() and fchownat() will be possible to use with dfd being an O_PATH-opened symlink and empty relative pathname. Combined with open_by_handle() it'll give us a way to do realink-by-handle and lchown-by-handle without messing with more redundant syscalls. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
parent
1abf0c718f
commit
bcda76524c
25
fs/namei.c
25
fs/namei.c
@ -766,8 +766,14 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p)
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error = 0;
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if (s)
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error = __vfs_follow_link(nd, s);
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else if (nd->last_type == LAST_BIND)
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else if (nd->last_type == LAST_BIND) {
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nd->flags |= LOOKUP_JUMPED;
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if (nd->path.dentry->d_inode->i_op->follow_link) {
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/* stepped on a _really_ weird one */
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path_put(&nd->path);
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error = -ELOOP;
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}
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}
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}
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return error;
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}
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@ -1954,6 +1960,10 @@ static int may_open(struct path *path, int acc_mode, int flag)
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struct inode *inode = dentry->d_inode;
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int error;
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/* O_PATH? */
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if (!acc_mode)
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return 0;
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if (!inode)
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return -ENOENT;
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@ -2056,7 +2066,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
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int open_flag = op->open_flag;
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int will_truncate = open_flag & O_TRUNC;
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int want_write = 0;
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int skip_perm = 0;
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int acc_mode = op->acc_mode;
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struct file *filp;
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struct inode *inode;
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int error;
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@ -2095,8 +2105,11 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
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}
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if (!(open_flag & O_CREAT)) {
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int symlink_ok = 0;
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if (nd->last.name[nd->last.len])
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nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
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if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
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symlink_ok = 1;
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/* we _can_ be in RCU mode here */
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error = do_lookup(nd, &nd->last, path, &inode);
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if (error) {
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@ -2108,7 +2121,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
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terminate_walk(nd);
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return ERR_PTR(-ENOENT);
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}
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if (unlikely(inode->i_op->follow_link)) {
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if (unlikely(inode->i_op->follow_link && !symlink_ok)) {
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/* We drop rcu-walk here */
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if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
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return ERR_PTR(-ECHILD);
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@ -2175,7 +2188,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
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/* Don't check for write permission, don't truncate */
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open_flag &= ~O_TRUNC;
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will_truncate = 0;
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skip_perm = 1;
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acc_mode = MAY_OPEN;
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error = security_path_mknod(&nd->path, dentry, mode, 0);
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if (error)
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goto exit_mutex_unlock;
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@ -2225,7 +2238,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
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want_write = 1;
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}
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common:
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error = may_open(&nd->path, skip_perm ? 0 : op->acc_mode, open_flag);
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error = may_open(&nd->path, acc_mode, open_flag);
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if (error)
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goto exit;
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filp = nameidata_to_filp(nd);
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@ -2358,7 +2371,7 @@ struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
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flags |= LOOKUP_ROOT;
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if (dentry->d_inode->i_op->follow_link)
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if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
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return ERR_PTR(-ELOOP);
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file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
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