[libvirt] [PATCH] conf: Add check to avoid a NULL compare for SysfsPath

[Cole Robinson]

On 01/18/2019 02:49 AM, Cheng Lin wrote:
> If the two sysfs_path are both NULL, there may be an incorrect
> object returned for virNodeDeviceObjListFindBySysfsPath().
> 
> This check exists in old interface virNodeDeviceFindBySysfsPath().
> e.g.
> virNodeDeviceFindBySysfsPath(virNodeDeviceObjListPtr devs,
>                              const char *sysfs_path)
> {
>     ...
>         if ((devs->objs[i]->def->sysfs_path != NULL) &&
>             (STREQ(devs->objs[i]->def->sysfs_path, sysfs_path))) {
>     ...
> }
> 
> Signed-off-by: Cheng Lin <cheng.lin130 at zte.com.cn>
> ---
>  src/conf/virnodedeviceobj.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/src/conf/virnodedeviceobj.c b/src/conf/virnodedeviceobj.c
> index c8ad131..2e40de5 100644
> --- a/src/conf/virnodedeviceobj.c
> +++ b/src/conf/virnodedeviceobj.c
> @@ -207,7 +207,8 @@ virNodeDeviceObjListFindBySysfsPathCallback(const void *payload,
>      int want = 0;
>  
>      virObjectLock(obj);
> -    if (STREQ_NULLABLE(obj->def->sysfs_path, sysfs_path))
> +    if ((obj->def->sysfs_path != NULL) &&
> +        (STREQ_NULLABLE(obj->def->sysfs_path, sysfs_path)))
>          want = 1;
>      virObjectUnlock(obj);
>      return want;
> 

Thanks, I reformatted to this and pushed:

@@ -207,7 +207,8 @@ virNodeDeviceObjListFindBySysfsPathCallback(const
void *payload,
     int want = 0;

     virObjectLock(obj);
-    if (STREQ_NULLABLE(obj->def->sysfs_path, sysfs_path))
+    if (obj->def->sysfs_path &&
+        STREQ_NULLABLE(obj->def->sysfs_path, sysfs_path))
         want = 1;
     virObjectUnlock(obj);
     return want;

What kind of devices are you seeing that don't have a sysfs_path I?
Seems like there's lots of places internally we expect it to be there,
but some others where we don't, so people must have hit similar issues
before, but I don't think I see an example in the udev output on my machine

- Cole