mysql-5.7.34 segfault in net_field_length_size

[Bugs SysSec]

Steps to reproduce this bug (see files attached):

```
$ cat /etc/os-release | grep VERSION=
VERSION="18.04.5 LTS (Bionic Beaver)"
$ mysql --version
mysql Ver 14.14 Distrib 5.7.34, for Linux (x86_64) using EditLine wrapper
$ python server_output.py | nc -vvvlp 3306 &
$ mysql --ssl-mode=DISABLED -h 127.0.0.1 -u root --password=root < stdin.txt
[...]
Segmentation fault (core dumped)
```

ASAN log of crash:
```
ASAN:DEADLYSIGNAL
=================================================================
==141==ERROR: AddressSanitizer: SEGV on unknown address 0x2bf27fffa12e (pc 0x0000004eac0d bp 0x7fffbf34db50 sp 0x7fffbf34d7e8 T0)
==141==The signal is caused by a READ memory access.
    #0 0x4eac0c in net_field_length_size /tmp/deb-src/mysql-5.7-5.7.34/sql-common/pack.c:198
    #1 0x4a8b40 in net_field_length_ll_safe /tmp/deb-src/mysql-5.7-5.7.34/sql-common/client.c:725
    #2 0x4a8b40 in read_ok_ex /tmp/deb-src/mysql-5.7-5.7.34/sql-common/client.c:823
    #3 0x4adfd2 in cli_read_query_result /tmp/deb-src/mysql-5.7-5.7.34/sql-common/client.c:4989
    #4 0x4b2b77 in mysql_real_query /tmp/deb-src/mysql-5.7-5.7.34/sql-common/client.c:5068
    #5 0x40d11d in server_version_string /tmp/deb-src/mysql-5.7-5.7.34/client/mysql.cc:5340
    #6 0x4075c8 in main /tmp/deb-src/mysql-5.7-5.7.34/client/mysql.cc:1357
    #7 0x7f42ceed0bf6 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)
    #8 0x4093a9 in _start (/mnt/mysql-asan+0x4093a9)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /tmp/deb-src/mysql-5.7-5.7.34/sql-common/pack.c:198 in net_field_length_size
==141==ABORTING
```

[Lucas Kanashiro (lucaskanashiro)]

Thank you for taking the time to report this bug and helping to make Ubuntu better.

I did reproduce what you mentioned and I got this segfault when running the mysql command:

root@mysql-triage:~# mysql --ssl-mode=DISABLED -h 127.0.0.1 -u root --password=root < stdin.txt
mysql: [Warning] Using a password on the command line interface can be insecure.
Connection from localhost 57006 received!
����!rootoR�~ˌ�N��5Ͻ�;�}mysql_native_passworde_osLinux
                                                      _client_namlibmysql_pid2890_client_version5.7.34 _platformx86_64
              program_namemysql!select @@version_comment limit 1mysql: Character set '' is not a compiled character set and is not specified in the '/usr/share/mysql/charsets/Index.xml' file
mysql: Character set '' is not a compiled character set and is not specified in the '/usr/share/mysql/charsets/Index.xml' file
mysql: Character set '' is not a compiled character set and is not specified in the '/usr/share/mysql/charsets/Index.xml' file
Segmentation fault (core dumped)

I did not go deep into debugging this but this does not seem related to a package issue. Have you tried to contact upstream about that? Explaining your goal, what was expected and what did you get. I am marking this bug as Incomplete for now until you provide more info explaining why do you think this is a bug in Ubuntu, when you do that please set the bug status back to New and we will revisit it.

[Launchpad Janitor (janitor)]

[Expired for mysql-5.7 (Ubuntu) because there has been no activity for 60 days.]