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Message-Id: <E1OHaMV-0008WK-PQ@pomaz-ex.szeredi.hu>
Date: Thu, 27 May 2010 12:30:51 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: Al Viro <viro@...IV.linux.org.uk>
CC: John Johansen <john.johansen@...onical.com>,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] vfs: show unreachable paths in getcwd and proc
From: Miklos Szeredi <mszeredi@...e.cz>
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@...e.cz>
---
fs/dcache.c | 82 +++++++++++++++++++++++++++++++++++++++++--------
fs/proc/base.c | 2 -
include/linux/dcache.h | 1
3 files changed, 72 insertions(+), 13 deletions(-)
Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c 2010-05-27 12:22:21.000000000 +0200
+++ linux-2.6/fs/dcache.c 2010-05-27 12:22:24.000000000 +0200
@@ -1957,6 +1957,33 @@ int __d_path(const struct path *path, st
return error;
}
+static void current_root(struct path *root)
+{
+ read_lock(¤t->fs->lock);
+ *root = current->fs->root;
+ path_get(root);
+ read_unlock(¤t->fs->lock);
+}
+
+static int __d_path_with_deleted(const struct path *path, struct path *root,
+ char **buffer, int *buflen)
+{
+ int error;
+
+ prepend(buffer, buflen, "\0", 1);
+ if (d_unlinked(path->dentry)) {
+ error = prepend(buffer, buflen, " (deleted)", 10);
+ if (error)
+ return error;
+ }
+ return __d_path(path, root, buffer, 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
@@ -1990,27 +2017,51 @@ char *d_path(const struct path *path, ch
if (path->dentry->d_op && path->dentry->d_op->d_dname)
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
- read_lock(¤t->fs->lock);
- root = current->fs->root;
- path_get(&root);
- read_unlock(¤t->fs->lock);
+ current_root(&root);
spin_lock(&dcache_lock);
ptr = buf + buflen;
- prepend(&ptr, &buflen, "\0", 1);
- if (d_unlinked(path->dentry)) {
- error = prepend(&ptr, &buflen, " (deleted)", 10);
- if (error)
- goto out;
- }
tmp = root;
- error = __d_path(path, &tmp, &ptr, &buflen);
-out:
+ error = __d_path_with_deleted(path, &tmp, &ptr, &buflen);
spin_unlock(&dcache_lock);
path_put(&root);
return error ? ERR_PTR(error) : ptr;
}
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 *ptr;
+ 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);
+
+ current_root(&root);
+ spin_lock(&dcache_lock);
+ ptr = buf + buflen;
+ tmp = root;
+ error = __d_path_with_deleted(path, &tmp, &ptr, &buflen);
+ if (!error) {
+ if (tmp.dentry != root.dentry || tmp.mnt != root.mnt)
+ error = prepend_unreachable(&ptr, &buflen);
+ }
+
+ spin_unlock(&dcache_lock);
+ path_put(&root);
+ return error ? ERR_PTR(error) : ptr;
+}
+
/*
* Helper function for dentry_operations.d_dname() members
*/
@@ -2118,6 +2169,13 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
if (error)
goto out;
+ /* Unreachable from current root */
+ if (tmp.dentry != root.dentry || tmp.mnt != root.mnt) {
+ error = prepend_unreachable(&cwd, &buflen);
+ if (error)
+ goto out;
+ }
+
error = -ERANGE;
len = PAGE_SIZE + page - cwd;
if (len <= size) {
Index: linux-2.6/include/linux/dcache.h
===================================================================
--- linux-2.6.orig/include/linux/dcache.h 2010-05-27 12:13:48.000000000 +0200
+++ linux-2.6/include/linux/dcache.h 2010-05-27 12:22:24.000000000 +0200
@@ -315,6 +315,7 @@ extern char *dynamic_dname(struct dentry
extern int __d_path(const struct path *path, struct path *root, char **, int *);
extern char *d_path(const struct path *, char *, int);
+extern char *d_path_with_unreachable(const struct path *, char *, int);
extern char *dentry_path(struct dentry *, char *, int);
/* Allocation counts.. */
Index: linux-2.6/fs/proc/base.c
===================================================================
--- linux-2.6.orig/fs/proc/base.c 2010-05-27 11:53:55.000000000 +0200
+++ linux-2.6/fs/proc/base.c 2010-05-27 12:22:24.000000000 +0200
@@ -1438,7 +1438,7 @@ static int do_proc_readlink(struct path
if (!tmp)
return -ENOMEM;
- pathname = d_path(path, tmp, PAGE_SIZE);
+ pathname = d_path_with_unreachable(path, tmp, PAGE_SIZE);
len = PTR_ERR(pathname);
if (IS_ERR(pathname))
goto out;
--
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