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[Qemu-devel] [PULL 13/28] 9pfs: local: utimensat: don't follow symlinks
From: |
Greg Kurz |
Subject: |
[Qemu-devel] [PULL 13/28] 9pfs: local: utimensat: don't follow symlinks |
Date: |
Tue, 28 Feb 2017 11:30:25 +0100 |
The local_utimensat() callback is vulnerable to symlink attacks because it
calls qemu_utimens()->utimensat(AT_SYMLINK_NOFOLLOW) which follows symbolic
links in all path elements but the rightmost one or qemu_utimens()->utimes()
which follows symbolic links for all path elements.
This patch converts local_utimensat() to rely on opendir_nofollow() and
utimensat(AT_SYMLINK_NOFOLLOW) directly instead of using qemu_utimens().
It is hence assumed that the OS supports utimensat(), i.e. has glibc 2.6
or higher and linux 2.6.22 or higher, which seems reasonable nowadays.
This partly fixes CVE-2016-9602.
Signed-off-by: Greg Kurz <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
---
hw/9pfs/9p-local.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 8fb79e44b5f3..a6dd77d7b895 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -959,13 +959,20 @@ static int local_chown(FsContext *fs_ctx, V9fsPath
*fs_path, FsCred *credp)
static int local_utimensat(FsContext *s, V9fsPath *fs_path,
const struct timespec *buf)
{
- char *buffer;
- int ret;
- char *path = fs_path->data;
+ char *dirpath = g_path_get_dirname(fs_path->data);
+ char *name = g_path_get_basename(fs_path->data);
+ int dirfd, ret = -1;
- buffer = rpath(s, path);
- ret = qemu_utimens(buffer, buf);
- g_free(buffer);
+ dirfd = local_opendir_nofollow(s, dirpath);
+ if (dirfd == -1) {
+ goto out;
+ }
+
+ ret = utimensat(dirfd, name, buf, AT_SYMLINK_NOFOLLOW);
+ close_preserve_errno(dirfd);
+out:
+ g_free(dirpath);
+ g_free(name);
return ret;
}
--
2.7.4
- [Qemu-devel] [PULL 03/28] 9pfs: remove side-effects in local_open() and local_opendir(), (continued)
- [Qemu-devel] [PULL 03/28] 9pfs: remove side-effects in local_open() and local_opendir(), Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 01/28] 9pfs: local: move xattr security ops to 9p-xattr.c, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 02/28] 9pfs: remove side-effects in local_init(), Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 05/28] 9pfs: local: keep a file descriptor on the shared folder, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 06/28] 9pfs: local: open/opendir: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 04/28] 9pfs: introduce relative_openat_nofollow() helper, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 09/28] 9pfs: local: lsetxattr: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 07/28] 9pfs: local: lgetxattr: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 08/28] 9pfs: local: llistxattr: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 12/28] 9pfs: local: remove: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 13/28] 9pfs: local: utimensat: don't follow symlinks,
Greg Kurz <=
- [Qemu-devel] [PULL 11/28] 9pfs: local: unlinkat: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 14/28] 9pfs: local: statfs: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 16/28] 9pfs: local: readlink: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 10/28] 9pfs: local: lremovexattr: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 15/28] 9pfs: local: truncate: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 17/28] 9pfs: local: lstat: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 19/28] 9pfs: local: rename: use renameat, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 18/28] 9pfs: local: renameat: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 20/28] 9pfs: local: improve error handling in link op, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 25/28] 9pfs: local: mknod: don't follow symlinks, Greg Kurz, 2017/02/28