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Re: [Qemu-devel] [PATCH 2/5] 9pfs: local: resolve special directories in
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 2/5] 9pfs: local: resolve special directories in paths |
Date: |
Fri, 5 May 2017 11:59:15 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.0 |
On 05/05/2017 09:37 AM, Greg Kurz wrote:
> When using the mapped-file security mode, the creds of a path /foo/bar
> are stored in the /foo/.virtfs_metadata/bar file. This is okay for all
> paths unless they end with '.' or '..', because we cannot create the
> corresponding file in the metadata directory.
>
> This patch ensures that '.' and '..' are resolved in all paths.
>
> The core code only passes path elements (no '/') to the backend, with
> the notable exception of the '/' path, which refers to the virtfs root.
> This patch preserve the current behavior of converting it to '.' so
s/preserve/preserves/
> that it can be passed to "*at()" syscalls ('/' would mean the host root).
>
> Signed-off-by: Greg Kurz <address@hidden>
> ---
> hw/9pfs/9p-local.c | 30 +++++++++++++++++++++++-------
> 1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
> index f3ebca4f7a56..92262f3c3e37 100644
> --- a/hw/9pfs/9p-local.c
> +++ b/hw/9pfs/9p-local.c
> @@ -1097,14 +1097,30 @@ static int local_name_to_path(FsContext *ctx,
> V9fsPath *dir_path,
> const char *name, V9fsPath *target)
> {
> if (dir_path) {
> - v9fs_path_sprintf(target, "%s/%s", dir_path->data, name);
> - } else if (strcmp(name, "/")) {
> - v9fs_path_sprintf(target, "%s", name);
> + if (!strcmp(name, ".")) {
> + /* "." relative to "foo/bar" is "foo/bar" */
> + v9fs_path_copy(target, dir_path);
> + } else if (!strcmp(name, "..")) {
> + if (!strcmp(dir_path->data, ".")) {
> + /* ".." relative to the root is "." */
> + v9fs_path_sprintf(target, ".");
> + } else {
> + char *tmp = g_path_get_dirname(dir_path->data);
> + /* ".." relative to "foo/bar" is equivalent to "foo" */
True only if bar is not a symlink to some other directory. What
guarantees do you have that you are not going to be inadvertently
skipping a traversal through symlinks and thereby picking the wrong
location for '..'?
> + v9fs_path_sprintf(target, "%s", tmp);
> + g_free(tmp);
> + }
> + } else {
> + assert(!strchr(name, '/'));
> + v9fs_path_sprintf(target, "%s/%s", dir_path->data, name);
> + }
> + } else if (!strcmp(name, "/") || !strcmp(name, ".") ||
> + !strcmp(name, "..")) {
> + /* This is the root fid */
> + v9fs_path_sprintf(target, ".");
> } else {
> - /* We want the path of the export root to be relative, otherwise
> - * "*at()" syscalls would treat it as "/" in the host.
> - */
> - v9fs_path_sprintf(target, "%s", ".");
> + assert(!strchr(name, '/'));
> + v9fs_path_sprintf(target, "./%s", name);
> }
> return 0;
> }
>
>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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[Qemu-devel] [PATCH 3/5] 9pfs: local: simplify file opening, Greg Kurz, 2017/05/05
[Qemu-devel] [PATCH 4/5] 9pfs: local: metadata file for the VirtFS root, Greg Kurz, 2017/05/05