[Qemu-devel] Re: [V9 PATCH 13/13] virtio-9p: Chroot environment for other functions

[Stefan Hajnoczi <stefanha@gmail.com>]

On Fri, Mar 18, 2011 at 08:58:01AM +0530, M. Mohan Kumar wrote:
> +static int get_dirfd(FsContext *fs_ctx, const char *path)
> +{
> +    int fd;
> +    char *dpath = qemu_strdup(path);
> +    char *last_component;
> +
> +    /* path can not contain ".." */
> +    last_component = strrchr(path, '/');
> +    if (last_component && !strcmp(last_component, "/..")) {
> +        error_report("9p path request contains \"..\": %s\n", path);
> +        qemu_free(dpath);
> +        errno = EFAULT;
> +        return -1;
> +    }
> +    fd = passthrough_request(fs_ctx, NULL, dirname(dpath), 0, NULL, T_OPEN);
> +    if (fd < 0) {
> +        qemu_free(dpath);
> +        errno = -fd;
> +        fd = -1;
> +    }
> +    return fd;
> +}

dpath is leaked in the success case.  I suggest writing the function like this:
static int get_dirfd(FsContext *fs_ctx, const char *path)
{
    int fd;
    char *dpath;
    char *last_component;

    /* path can not contain ".." */
    last_component = strrchr(path, '/');
    if (last_component && !strcmp(last_component, "/..")) {
        error_report("9p path request contains \"..\": %s\n", path);
        errno = EFAULT;
        return -1;
    }
    dpath = qemu_strdup(path);
    fd = passthrough_request(fs_ctx, NULL, dirname(dpath), 0, NULL, T_OPEN);
    qemu_free(dpath);
    if (fd < 0) {
        errno = -fd;
        fd = -1;
    }
    return fd;
}

> -static int local_utimensat(FsContext *s, const char *path,
> -                           const struct timespec *buf)
> +static int local_utimensat(FsContext *fs_ctx, const char *path,
> +                const struct timespec *buf)
>  {
> -    return qemu_utimensat(AT_FDCWD, rpath(s, path), buf, AT_SYMLINK_NOFOLLOW);
> +    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
> +        int fd, retval;
> +        fd = passthrough_request(fs_ctx, NULL, path,
> +                        O_RDONLY | O_NONBLOCK | O_NOFOLLOW, NULL, T_OPEN);
> +        if (fd < 0) {
> +            errno = -fd;
> +            return -1;
> +        }
> +        retval = futimens(fd, buf);
> +        close(fd);
> +        return retval;

errno is clobbered here.

Stefan