2012/10/1 Michal Privoznik <mprivozn@redhat.com>:
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
libcurl supports different DNS backends. This problem only affects the synchronous one where libcurl uses the described timeout mechanism. The asynchronous c-ares backend is not affected. But as I don't see a better solution to avoid the thread-unsafety of the SIGALRM/sigsetjmp/siglongjmp combination I'll push thins one. Thanks. -- Matthias Bolte http://photron.blogspot.com