vfs: show unreachable paths in getcwd and proc
Prepend "(unreachable)" to path strings if the path is not reachable
from the current root.
Two places updated are
- the return string from getcwd()
- and symlinks under /proc/$PID.
Other uses of d_path() are left unchanged (we know that some old
software crashes if /proc/mounts is changed).
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index 7fccb00..166d35d 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2019,6 +2019,11 @@
return prepend_path(path, root, buf, buflen);
}
+static int prepend_unreachable(char **buffer, int *buflen)
+{
+ return prepend(buffer, buflen, "(unreachable)", 13);
+}
+
/**
* d_path - return the path of a dentry
* @path: path to report
@@ -2064,6 +2069,39 @@
}
EXPORT_SYMBOL(d_path);
+/**
+ * d_path_with_unreachable - return the path of a dentry
+ * @path: path to report
+ * @buf: buffer to return value in
+ * @buflen: buffer length
+ *
+ * The difference from d_path() is that this prepends "(unreachable)"
+ * to paths which are unreachable from the current process' root.
+ */
+char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
+{
+ char *res = buf + buflen;
+ struct path root;
+ struct path tmp;
+ int error;
+
+ if (path->dentry->d_op && path->dentry->d_op->d_dname)
+ return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
+
+ get_fs_root(current->fs, &root);
+ spin_lock(&dcache_lock);
+ tmp = root;
+ error = path_with_deleted(path, &tmp, &res, &buflen);
+ if (!error && !path_equal(&tmp, &root))
+ error = prepend_unreachable(&res, &buflen);
+ spin_unlock(&dcache_lock);
+ path_put(&root);
+ if (error)
+ res = ERR_PTR(error);
+
+ return res;
+}
+
/*
* Helper function for dentry_operations.d_dname() members
*/
@@ -2173,15 +2211,23 @@
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
struct path tmp = root;
- char * cwd;
+ char *cwd = page + PAGE_SIZE;
+ int buflen = PAGE_SIZE;
- cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
+ prepend(&cwd, &buflen, "\0", 1);
+ error = prepend_path(&pwd, &tmp, &cwd, &buflen);
spin_unlock(&dcache_lock);
- error = PTR_ERR(cwd);
- if (IS_ERR(cwd))
+ if (error)
goto out;
+ /* Unreachable from current root */
+ if (!path_equal(&tmp, &root)) {
+ error = prepend_unreachable(&cwd, &buflen);
+ if (error)
+ goto out;
+ }
+
error = -ERANGE;
len = PAGE_SIZE + page - cwd;
if (len <= size) {