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Re: [libvirt] [PATCH] esx: Disable libcurl's use of signals to fix a segfault



On 29.09.2012 22:17, Matthias Bolte wrote:
> libcurl uses a SIGALRM in combination with sigsetjmp/siglongjmp to be
> able to abort a DNS lookup when it takes too long. The problem with this
> in a multi-threaded application is that the signal handler for SIGALRM
> and the call to siglongjmp can be executed on a thread that is different
> from the one that initially did the SIGALRM setup and the call to
> sigsetjmp. In the reported case this triggered a segfault.
> 
> Disable libcurl's use of signals to avoid this situation. This has the
> disadvantage of losing the ability to abort DNS lookups which might result
> in libcurl getting stuck in a DNS lookup in the worst case.
> 
> Reported by Benjamin Wang.
> ---
> 
>  src/esx/esx_vi.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/src/esx/esx_vi.c b/src/esx/esx_vi.c
> index 275b858..125eaee 100644
> --- a/src/esx/esx_vi.c
> +++ b/src/esx/esx_vi.c
> @@ -330,6 +330,7 @@ esxVI_CURL_Connect(esxVI_CURL *curl, esxUtil_ParsedUri *parsedUri)
>      }
>  
>      curl_easy_setopt(curl->handle, CURLOPT_USERAGENT, "libvirt-esx");
> +    curl_easy_setopt(curl->handle, CURLOPT_NOSIGNAL, 1);
>      curl_easy_setopt(curl->handle, CURLOPT_HEADER, 0);
>      curl_easy_setopt(curl->handle, CURLOPT_FOLLOWLOCATION, 0);
>      curl_easy_setopt(curl->handle, CURLOPT_SSL_VERIFYPEER,
> 

I think this is safe; From the version 7.10 curl can still timeout on
DNS lookup even with CURLOPT_NOSIGNAL set:

   http://curl.haxx.se/libcurl/c/curl_easy_setopt.html#CURLOPTNOSIGNAL

So ACK.

Michal


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