[PATCH 05/43] esx: convert virMutex to GMutex

[Pino Toscano]

On Friday, 10 April 2020 15:54:32 CEST Rafael Fonseca wrote:
> @@ -346,11 +342,12 @@ esxStreamClose(virStreamPtr stream, bool finish)
>  {
>      int result = 0;
>      esxStreamPrivate *priv = stream->privateData;
> +    g_autoptr(GMutexLocker) locker = NULL;
>  
>      if (!priv)
>          return 0;
>  
> -    virMutexLock(&priv->curl->lock);
> +    locker = g_mutex_locker_new(&priv->curl->lock);
>  
>      if (finish && priv->backlog_used > 0) {
>          virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> @@ -360,8 +357,6 @@ esxStreamClose(virStreamPtr stream, bool finish)
>  
>      stream->privateData = NULL;
>  
> -    virMutexUnlock(&priv->curl->lock);
> -
>      esxFreeStreamPrivate(&priv);

Careful here, this is a problematic situation:
- the lock is indirectly part of the @priv structure
- esxFreeStreamPrivate calls esxVI_CURL_Free(priv->curl)
- esxVI_CURL_Free calls virMutexDestroy(&item->lock)
- lock is still locked, so it will deadlock (or crash, or something
  not good anyway)

You must unlock the mutex before esxFreeStreamPrivate is called.

I did not check other patches of this long series for similar potential
issues, please do check them.

> diff --git a/src/esx/esx_vi.c b/src/esx/esx_vi.c
> index 16690edfbe..ed6c6c28cd 100644
> --- a/src/esx/esx_vi.c
> +++ b/src/esx/esx_vi.c
> @@ -433,14 +429,13 @@ int
>  esxVI_CURL_Upload(esxVI_CURL *curl, const char *url, const char *content)
>  {
>      int responseCode = 0;
> +    g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&curl->lock);
>  
>      if (!content) {
>          virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("Invalid argument"));
>          return -1;
>      }
>  
> -    virMutexLock(&curl->lock);
> -

Careful #2 here about locking earlier: while usually this is not an
issue, it could be in case the code that was executed without the lock
held can be called by other code branches with the lock held.

Again, this must be thoroughly checked in the whole patch series.

-- 
Pino Toscano
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