Re: Periodic segfault in curl_easy_perform()

From: Adrián Gimeno Balaguer via curl-library <curl-library_at_cool.haxx.se>
Date: Tue, 9 Mar 2021 15:23:59 +0100

El mié, 10 feb 2021 a las 16:10, Groke, Paul (<paul.groke_at_dynatrace.com>)
escribió:

> From: curl-library <curl-library-bounces_at_cool.haxx.se> On Behalf Of
> Adrián Gimeno Balaguer via curl-library
> Sent: Mittwoch, 10. Februar 2021 13:36
> To: curl-library_at_cool.haxx.se
> >
> > The program crashes after 5-10 minutes since startup (provided the
> periodic check always sends files) at curl_easy_perform() with the
> following stack trace:
> >
> > Program terminated with signal 11, Segmentation fault.
> > #0 0x00007ff9f8cddaec in free () from /lib64/libc.so.6
> > (gdb) bt
> > #0 0x00007ff9f8cddaec in free () from /lib64/libc.so.6
> > #1 0x00007ff9f984e3a1 in pthread_create_at__at_GLIBC_2.2.5 () from
> /lib64/libpthread.so.0
> > #2 0x00000000004b315c in Curl_thread_create ()
>
> Crashes in `free` usually mean there's heap corruption. And with heap
> corruptions, the stack-trace of the crash often has nothing to do with the
> actual bug. The most likely reasons for heap corruptions are out-of-bounds
> writes and use of dangling pointers. Daniel's suggestion to use
> valgrind/ASAN is a good one - those tools should help you find the cause.
> Count yourself lucky that you can repro the problem by just running the
> program for 5-10 minutes 😉
>
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>


Hello again,

After making functional changes in my program, I'm running into a different
crash scenario.

Program seems to run fine when sending a file in development machine, but
now it always crashes on a test machine with identical environment:

Program terminated with signal 11, Segmentation fault.
#0 __GI___libc_free (mem=0x1) at malloc.c:2941
2941 if (chunk_is_mmapped(p)) /* release mmapped
memory. */
(gdb) bt full
#0 __GI___libc_free (mem=0x1) at malloc.c:2941
        ar_ptr = <optimized out>
        p = <optimized out>
        hook = 0x0
#1 0x00000000004b070f in Curl_free_request_state ()
No symbol table info available.
#2 0x00000000004b1032 in Curl_connect ()
No symbol table info available.
#3 0x00000000004a4fbd in multi_runsingle ()
No symbol table info available.
#4 0x00000000004a59fe in curl_multi_perform ()
No symbol table info available.
#5 0x000000000049cd73 in curl_easy_perform ()
No symbol table info available.

I already tried to run Valgrind to debug the other "5-10 minutes" reported
crash I had before but couldn't reach anything useful on the development
machine, since it just kept running.

Could this stack trace mean any well-known mistake on CURL in this case?

Otherwise. Considering the fact that apparently Valgrind is aimed to detect
memory leaks and it can't (easily?) detect the source code line/s that
might cause deferred UB errors, should I even bother to install and run it
on the test machine? If so, should I use any special parameters?

Thanks,

-- 
*Adrián*

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Received on 2021-03-09