On 3/24/2018 1:34 AM, Gangadhar Hariharan wrote:
> I am using 2 threads. One for adding curl handle to multi-handle and
> the other to execute the multi_perform. i have a recursive mutex to
> safeguard the adding/executing of the multi-handle.
> In one of the executions, i see a crash in curl_multi_perform() with a
> stack frame at Curl_ssl_connect_nonblocking. i have never seen this
> before and i have been running my applications successfully for over 4
> months.
> Any inputs will be appreciated
>
> thread1:
>
> take_recursive_mutex_lock(r_mx);
> curl_multi_add_handle(mh, eh);
> release_recursive_lock(r_mx);
> ------------
>
> thread2:
>
> take_recursive_mutex_lock(r_mx);
> mret = curl_multi_perform(mh, &still_running);
> release_recursive_lock(r_mx);
> -----------
>
>
> It is observed that, thread1 is waiting on thread2 to release the lock
> and in thread2, there is a crash in curl_multi_perform():
> I see a frame at Curl_ssl_connect_nonblocking. Not sure why this would
> crash!
>
> (gdb) thread 2
> [Switching to thread 2 (Thread 0xb14c1440 (LWP 7180))]
> #0  0x1004e1fc in pal_sigsegv ()
> (gdb) bt
> #0  0x1004e1fc in pal_sigsegv ()
> #1  <signal handler called>
> #2  _asn1_copy_structure3 (source_node=source_node_at_entry=0x119ae3e8)
>     at
> /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/minitasn1/structure.c:426
> #3  0x0f62f6d4 in _asn1_append_sequence_set (node=<optimized out>,
>     ptail=ptail_at_entry=0xb14c0850)
>     at
> /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/minitasn1/element.c:155
> #4  0x0f62aaac in asn1_der_decoding2 (element=element_at_entry=0x10c11f58,
>     ider=0x119af648, max_ider_len=max_ider_len_at_entry=0xb14c08f8,
>     flags=flags_at_entry=2, errorDescription=errorDescription_at_entry=0x0)
>     at
> /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/minitasn1/decoding.c:1440
> #5  0x0f5d8804 in _asn1_strict_der_decode (errorDescription=0x0, len=1359,
>     ider=<optimized out>, element=0x10c11f58)
>     at
> /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/x509/common.h:252
> #6  gnutls_x509_crt_import (cert=0x10c11f58, data=data_at_entry=0xb14c0978,
>     format=format_at_entry=GNUTLS_X509_FMT_PEM)
>     at /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/x509/x509.c:310
> #7  0x0f5dd160 in gnutls_x509_crt_list_import (certs=0x5d518710,
>     cert_max=cert_max_at_entry=0xb14c09d8, data=data_at_entry=0xb14c0a60,
>     format=format_at_entry=GNUTLS_X509_FMT_PEM, flags=flags_at_entry=1)
>     at /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/x509/x509.c:3365
> #8  0x0f5dd4c4 in gnutls_x509_crt_list_import2
> (certs=certs_at_entry=0xb14c0a24,
>     size=size_at_entry=0xb14c0a1c, data=data_at_entry=0xb14c0a60,
>     format=format_at_entry=GNUTLS_X509_FMT_PEM, flags=flags_at_entry=0)
>     at /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/x509/x509.c:3244
> #9  0x0f5e51ec in gnutls_x509_trust_list_add_trust_mem (
>     list=list_at_entry=0x5d517af8, cas=cas_at_entry=0xb14c0a60,
>     crls=crls_at_entry=0xb14c0a58, type=type_at_entry=GNUTLS_X509_FMT_PEM,
>     tl_flags=tl_flags_at_entry=2, tl_vflags=tl_vflags_at_entry=0)
>     at
> /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/x509/verify-high2.c:80
> #10 0x0f5e55d0 in gnutls_x509_trust_list_add_trust_file (list=0x5d517af8,
>     ca_file=<optimized out>, crl_file=crl_file_at_entry=0x0,
>     type=type_at_entry=GNUTLS_X509_FMT_PEM, tl_flags=tl_flags_at_entry=2,
>     tl_vflags=tl_vflags_at_entry=0)
>     at
> /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/x509/verify-high2.c:362
> #11 0x0f5976fc in gnutls_certificate_set_x509_trust_file (
>     cred=<optimized out>, cafile=<optimized out>,
>     type=type_at_entry=GNUTLS_X509_FMT_PEM)
>     at
> /work/mysrc/debug/gnutls/3.4.9-r0/gnutls-3.4.9/lib/gnutls_x509.c:1611
> #12 0x0fbe7758 in gtls_connect_step1 (sockindex=0, conn=0x5cccc500)
>     at /work/mysrc/debug/curl/7.47.1-r0/curl-7.47.1/lib/vtls/gtls.c:458
> #13 gtls_connect_common (conn=0x5cccc500, sockindex=0,
>     nonblocking=<optimized out>, done=0xb14c0b92)
>     at /work/mysrc/debug/curl/7.47.1-r0/curl-7.47.1/lib/vtls/gtls.c:1321
> #14 0x0fbe8b80 in Curl_ssl_connect_nonblocking
> (conn=conn_at_entry=0x5cccc500,
>     sockindex=sockindex_at_entry=0, done=done_at_entry=0xb14c0b92)
>     at /work/mysrc/debug/curl/7.47.1-r0/curl-7.47.1/lib/vtls/vtls.c:333
> #15 0x0fbb2460 in https_connecting (done=0xb14c0b92, conn=0x5cccc500)
>     at /work/mysrc/debug/curl/7.47.1-r0/curl-7.47.1/lib/http.c:1386
> #16 Curl_http_connect (conn=0x5cccc500, done=0xb14c0b92)
>     at /work/mysrc/debug/curl/7.47.1-r0/curl-7.47.1/lib/http.c:1356
> #17 0x0fbc4890 in Curl_protocol_connect (conn=0x5cccc500,
>     protocol_done=protocol_done_at_entry=0xb14c0b92)
>     at /work/mysrc/debug/curl/7.47.1-r0/curl-7.47.1/lib/url.c:3668
> #18 0x0fbd5f48 in multi_runsingle (multi=0x106156e8, multi_at_entry=0x0,
>     now=<error reading variable: value has been optimized out>,
>     data=data_at_entry=0x119fc760)
>     at /work/mysrc/debug/curl/7.47.1-r0/curl-7.47.1/lib/multi.c:1264
> #19 0x0fbd6b50 in curl_multi_perform (multi_handle=0x0,
> running_handles=0x0)
>     at /work/mysrc/debug/curl/7.47.1-r0/curl-7.47.1/lib/multi.c:1821
> #20 0x10041604 in my_thread ()
> #21 0x0ffc3ec0 in start_my_thread (arg=0xb14c1440)
>     at /work/mysrc/debug/glibc/2.23-r0/git/nptl/pthread_create.c:335
> #22 0x0f7936c4 in clone () from /lib/libc.so.6
> (gdb)​​

Are you using any other function that accesses the multi handle
unprotected? Also the easy handle you are adding has the same
restrictions as the multi handle. Please review
https://curl.haxx.se/libcurl/c/threadsafe.html

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Received on 2018-03-24