$ ostree init --repo=/tmp/test/repo
$ ostree --repo=/tmp/test/repo remote add --no-gpg-verify mojefedora https://firefox-flatpak.mojefedora.cz/repo/
$ ostree --repo=/tmp/test/repo pull --depth=-1 --mirror mojefedora
> Receiving metadata objects: 999/(estimating) 15.2 kB/s 319.6 kB
> Segmentation fault (core dumped)

#0  0x00007f7d5dcfeabe in multi_socket (multi=multi@entry=0x565254bf6000, checkall=checkall@entry=false, s=<optimized out>, ev_bitmask=1, running_handles=running_handles@entry=0x565254bf9160) at ../../lib/multi.c:2574
#1  0x00007f7d5dcfedab in curl_multi_socket_action (multi=0x565254bf6000, s=<optimized out>, ev_bitmask=<optimized out>, running_handles=running_handles@entry=0x565254bf9160) at ../../lib/multi.c:2760
#2  0x00007f7d5e84232a in event_cb (fd=<optimized out>, condition=<optimized out>, data=0x565254bf90e0) at src/libostree/ostree-fetcher-curl.c:451
#3  0x00007f7d5e4a9f40 in g_main_context_dispatch () at /lib64/libglib-2.0.so.0
#4  0x00007f7d5e4aa2d8 in g_main_context_iterate.isra () at /lib64/libglib-2.0.so.0
#5  0x00007f7d5e4aa383 in g_main_context_iteration () at /lib64/libglib-2.0.so.0
#6  0x00007f7d5e8097d5 in ostree_repo_pull_with_options (self=<optimized out>, remote_name_or_baseurl=<optimized out>, options=options@entry=0x565254bf5b30, progress=progress@entry=0x565254be5240, cancellable=cancellable@entry=0x0, error
=error@entry=0x7ffea2cd61d8) at src/libostree/ostree-repo-pull.c:4491
#7  0x0000565253e22637 in ostree_builtin_pull (argc=<optimized out>, argv=<optimized out>, invocation=<optimized out>, cancellable=0x0, error=0x7ffea2cd61d8) at src/ostree/ot-builtin-pull.c:370
#8  0x0000565253e1a6b0 in ostree_run (argc=<optimized out>, argv=<optimized out>, commands=0x565253e40020 <commands>, res_error=0x7ffea2cd6230) at src/ostree/ot-main.c:202
#9  0x0000565253e0b84d in main (argc=6, argv=0x7ffea2cd6348) at src/ostree/main.c:138

2526│ static CURLMcode multi_socket(struct Curl_multi *multi,
2527│                               bool checkall,
2528│                               curl_socket_t s,
2529│                               int ev_bitmask,
2530│                               int *running_handles)
2531│ {
2532│   CURLMcode result = CURLM_OK;
2533│   struct Curl_easy *data = NULL;
2534│   struct Curl_tree *t;
2535│   struct curltime now = Curl_now();
2536│
2537│   if(checkall) {
2538│     /* *perform() deals with running_handles on its own */
2539│     result = curl_multi_perform(multi, running_handles);
2540│
2541│     /* walk through each easy handle and do the socket state change magic
2542│        and callbacks */
2543│     if(result != CURLM_BAD_HANDLE) {
2544│       data = multi->easyp;
2545│       while(data && !result) {
2546│         result = singlesocket(multi, data);
2547│         data = data->next;
2548│       }
2549│     }
2550│
2551│     /* or should we fall-through and do the timer-based stuff? */
2552│     return result;                                               
2553│   }
2554│   if(s != CURL_SOCKET_TIMEOUT) {
2555│
2556│     struct Curl_sh_entry *entry = sh_getentry(&multi->sockhash, s);
2557│
2558│     if(!entry)
2559│       /* Unmatched socket, we can't act on it but we ignore this fact.  In
2560│          real-world tests it has been proved that libevent can in fact give
2561│          the application actions even though the socket was just previously
2562│          asked to get removed, so thus we better survive stray socket actions
2563│          and just move on. */
2564│       ;
2565│     else {
2566│       struct curl_llist *list = &entry->list;
2567│       struct curl_llist_element *e;
2568│       SIGPIPE_VARIABLE(pipe_st);
2569│
2570│       /* the socket can be shared by many transfers, iterate */
2571│       for(e = list->head; e; e = e->next) {
2572│         data = (struct Curl_easy *)e->ptr;
2573│
2574├>        if(data->magic != CURLEASY_MAGIC_NUMBER)
2575│           /* bad bad bad bad bad bad bad */
2576│           return CURLM_INTERNAL_ERROR;

(gdb) p	data
> $1 = (struct Curl_easy *) 0x0


$ rpm -q ostree ostree-libs libcurl
> ostree-2019.2-1.fc31.x86_64
> ostree-libs-2019.2-1.fc31.x86_64
> libcurl-7.64.1-2.fc31.x86_64