Re: [RFC v2 13/15] vfio/iommufd: Implement the iommufd backend

[Eric Auger]

Hi Alister,
On 10/4/22 08:47, Alistair Popple wrote:
> Yi Liu <yi.l.liu@intel.com> writes:
>
> [...]
>
>> +static int vfio_get_devicefd(const char *sysfs_path, Error **errp)
>> +{
>> +    long int ret = -ENOTTY;
>> +    char *path, *vfio_dev_path = NULL, *vfio_path = NULL;
>> +    DIR *dir;
>> +    struct dirent *dent;
>> +    gchar *contents;
>> +    struct stat st;
>> +    gsize length;
>> +    int major, minor;
>> +    dev_t vfio_devt;
>> +
>> +    path = g_strdup_printf("%s/vfio-device", sysfs_path);
>> +    if (stat(path, &st) < 0) {
>> +        error_setg_errno(errp, errno, "no such host device");
>> +        goto out_free_path;
>> +    }
>> +
>> +    dir = opendir(path);
>> +    if (!dir) {
>> +        error_setg_errno(errp, errno, "couldn't open dirrectory %s", path);
>> +        goto out_free_path;
>> +    }
>> +
>> +    while ((dent = readdir(dir))) {
>> +        if (!strncmp(dent->d_name, "vfio", 4)) {
>> +            vfio_dev_path = g_strdup_printf("%s/%s/dev", path, 
>> dent->d_name);
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (!vfio_dev_path) {
>> +        error_setg(errp, "failed to find vfio-device/vfioX/dev");
>> +        goto out_free_path;
>> +    }
>> +
>> +    if (!g_file_get_contents(vfio_dev_path, &contents, &length, NULL)) {
>> +        error_setg(errp, "failed to load \"%s\"", vfio_dev_path);
>> +        goto out_free_dev_path;
>> +    }
>> +
>> +    if (sscanf(contents, "%d:%d", &major, &minor) != 2) {
>> +        error_setg(errp, "failed to get major:mino for \"%s\"", 
>> vfio_dev_path);
>> +        goto out_free_dev_path;
>> +    }
>> +    g_free(contents);
>> +    vfio_devt = makedev(major, minor);
>> +
>> +    vfio_path = g_strdup_printf("/dev/vfio/devices/%s", dent->d_name);
>> +    ret = open_cdev(vfio_path, vfio_devt);
>> +    if (ret < 0) {
>> +        error_setg(errp, "Failed to open %s", vfio_path);
>> +    }
>> +
>> +    trace_vfio_iommufd_get_devicefd(vfio_path, ret);
>> +    g_free(vfio_path);
>> +
>> +out_free_dev_path:
>> +    g_free(vfio_dev_path);
>> +out_free_path:
>> +    g_free(path);
>> +
>> +    if (*errp) {
>> +        error_prepend(errp, VFIO_MSG_PREFIX, path);
> I ran into this while trying to get things running, so haven't reviewed
> the patch but noticed path is used after it's freed if !!*errp.

thank you for the bug report! We will fix that on the next iteration.

Eric
>
>  - Alistair
>
>> +    }
>> +    return ret;
>> +}