Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754840Ab0FDLx5 (ORCPT ); Fri, 4 Jun 2010 07:53:57 -0400 Received: from fxip-0047f.externet.hu ([88.209.222.127]:49412 "EHLO pomaz-ex.szeredi.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753915Ab0FDLx4 (ORCPT ); Fri, 4 Jun 2010 07:53:56 -0400 To: Al Viro , Andrew Morton CC: John Johansen , Tetsuo Handa , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org In-reply-to: (message from Miklos Szeredi on Fri, 04 Jun 2010 13:52:12 +0200) Subject: [PATCH 2/2] vfs: show unreachable paths in getcwd and proc References: Message-Id: From: Miklos Szeredi Date: Fri, 04 Jun 2010 13:53:42 +0200 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5101 Lines: 165 From: Miklos Szeredi 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 --- 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/