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Date: Tue, 15 Jun 2010 09:31:51 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: viro@...IV.linux.org.uk
CC: akpm@...ux-foundation.org, john.johansen@...onical.com,
penguin-kernel@...ove.SAKURA.ne.jp, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] vfs: show unreachable paths in getcwd and proc
Hi Al,
Could you please consider these patches for 2.6.36?
Thanks,
Miklos
On Fri, 04 Jun 2010, Miklos Szeredi wrote:
> 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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