segfault in uftrace tui

[honggyukim]

Here is the gdb backtrace info.

$ gdb -q --args uftrace tui
    ...
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff68363c7 in memcpy () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007ffff68363c7 in memcpy () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007ffff681fd8f in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#2  0x00007ffff6814469 in fread () from /lib/x86_64-linux-gnu/libc.so.6
#3  0x00005555555a79ff in __read_task_ustack (task=0x555556935ed8) at /home/honggyu/work/uftrace/utils/fstack.c:1017
#4  0x00005555555a8ba7 in read_task_ustack (handle=0x7fffffffd9b0, task=0x555556935ed8) at /home/honggyu/work/uftrace/utils/fstack.c:1399
#5  0x00005555555a9278 in get_task_ustack (handle=0x7fffffffd9b0, idx=1) at /home/honggyu/work/uftrace/utils/fstack.c:1453
#6  0x00005555555a933a in read_user_stack (handle=0x7fffffffd9b0, task=0x7fffffffd8e0) at /home/honggyu/work/uftrace/utils/fstack.c:1591
#7  0x00005555555aa671 in __read_rstack (handle=0x7fffffffd9b0, taskp=0x7fffffffd9a0, consume=true) at /home/honggyu/work/uftrace/utils/fstack.c:2060
#8  0x00005555555aac3e in read_rstack (handle=0x7fffffffd9b0, task=0x7fffffffd9a0) at /home/honggyu/work/uftrace/utils/fstack.c:2208
#9  0x0000555555574e71 in command_tui (argc=0, argv=0x7fffffffde58, opts=0x7fffffffdc00) at /home/honggyu/work/uftrace/cmds/tui.c:2625
#10 0x0000555555561554 in main (argc=0, argv=0x7fffffffde58) at /home/honggyu/work/uftrace/uftrace.c:1208

The source location is

1013│ static int __read_task_ustack(struct uftrace_task_reader *task)
1014│ {
1015│         FILE *fp = task->fp;
1016│
1017├───────> if (fread(&task->ustack, sizeof(task->ustack), 1, fp) != 1) {
1018│                 if (feof(fp))
1019│                         return -1;
1020│
1021│                 pr_warn("error reading rstack: %s\n", strerror(errno));
1022│                 return -1;
1023│         }
1024│
1025│         if (task->h->needs_byte_swap)
1026│                 swap_byte_order(&task->ustack);
1027│         if (task->h->needs_bit_swap)
1028│                 swap_bitfields(&task->ustack);
1029│
1030│         if (task->ustack.magic != RECORD_MAGIC) {
1031│                 pr_warn("invalid rstack read\n");
1032│                 return -1;
1033│         }
1034│
1035│         return 0;
1036│ }
1037│
/home/honggyu/work/uftrace/utils/fstack.c