Core was generated by `nginx: worker process                   '.
Program terminated with signal 11, Segmentation fault.
#0  0x000000000040af99 in ngx_vslprintf (buf=0x7fffce908963 "\316\002", last=0x7fffce909130 "", fmt=<value optimized out>, 
    args=0x7fffce908910) at src/core/ngx_string.c:254
254	                    while (*p && buf < last) {
(gdb) bt
#0  0x000000000040af99 in ngx_vslprintf (buf=0x7fffce908963 "\316\002", last=0x7fffce909130 "", fmt=<value optimized out>, 
    args=0x7fffce908910) at src/core/ngx_string.c:254
#1  0x0000000000406bfe in ngx_log_error_core (level=3, log=0x1bcbf960, err=14, fmt=0x47f5c0 "chmod() \"%s\" failed")
    at src/core/ngx_log.c:120
#2  0x000000000040e562 in ngx_ext_rename_file (src=0x1bdb2540, to=0x1bdb1c98, ext=0x7fffce909330) at src/core/ngx_file.c:557
#3  0x000000000045153a in ngx_http_file_cache_update (r=0x1bcbf9e8, tf=0x1bdb2538) at src/http/ngx_http_file_cache.c:938
#4  0x0000000000446ed6 in ngx_http_upstream_process_request (r=0x1bcbf9e8) at src/http/ngx_http_upstream.c:2686
#5  0x000000000044a068 in ngx_http_upstream_send_response (r=0x1bcbf9e8, u=0x1bdb1930) at src/http/ngx_http_upstream.c:2342
#6  ngx_http_upstream_process_header (r=0x1bcbf9e8, u=0x1bdb1930) at src/http/ngx_http_upstream.c:1644
#7  0x00000000004471d9 in ngx_http_upstream_handler (ev=0x1bcd83f0) at src/http/ngx_http_upstream.c:935
#8  0x000000000041d7b4 in ngx_event_process_posted (cycle=0x1bbca0c0, posted=0x6aec68) at src/event/ngx_event_posted.c:40
#9  0x0000000000424646 in ngx_worker_process_cycle (cycle=0x1bbca0c0, data=<value optimized out>) at src/os/unix/ngx_process_cycle.c:808
#10 0x0000000000422bfd in ngx_spawn_process (cycle=0x1bbca0c0, proc=0x424580 <ngx_worker_process_cycle>, data=0x0, 
    name=0x4823ce "worker process", respawn=-3) at src/os/unix/ngx_process.c:198
#11 0x0000000000423b7c in ngx_start_worker_processes (cycle=0x1bbca0c0, n=96, type=-3) at src/os/unix/ngx_process_cycle.c:365
#12 0x0000000000424e14 in ngx_master_process_cycle (cycle=0x1bbca0c0) at src/os/unix/ngx_process_cycle.c:137
#13 0x0000000000406795 in main (argc=-829384832, argv=<value optimized out>) at src/core/nginx.c:410