mysqld crash when config not readable

[Elan Ruusamäe]

mysql-5.5.27-1.x86_64

# ls -l /etc/mysql/delfiua.conf
-rw-r----- 1 root root 5616 okt 31 16:23 /etc/mysql/delfiua.conf

mysql> slave start;

Could not open required defaults file: /etc/mysql/delfiua.conf
Fatal error in defaults handling. Program aborted
*** glibc detected *** /usr/sbin/mysqld: free(): invalid pointer: 0x00007fa1500085e0 ***
121031 16:23:59 [Note] Slave SQL thread initialized, starting replication in log 'FIRST' at position 0, relay log './slave-relay-bin.000001' position: 4
Query OK, 0 rows affected (0.00 sec)

mysql> ======= Backtrace: =========
/lib64/libc.so.6(+0x79df6)[0x7fa166956df6]
/usr/sbin/mysqld(free_root+0x3d)[0x771f3d]
/usr/sbin/mysqld(free_defaults+0x4c)[0x7645dc]
/usr/sbin/mysqld(mysql_read_default_options+0x10a)[0x65d3ca]
/usr/sbin/mysqld(mysql_init+0xb5)[0x65df35]
/usr/sbin/mysqld(handle_slave_io+0x59f)[0x543aef]
/lib64/libpthread.so.0(+0x8034)[0x7fa168715034]
/lib64/libc.so.6(clone+0x6d)[0x7fa1669c57ad]
======= Memory map: ========
14:23:59 UTC - mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.
Please help us make Percona Server better by reporting any
bugs at http://bugs.percona.com/

key_buffer_size=8388608
read_buffer_size=131072
max_used_connections=1
max_threads=151
thread_count=1
connection_count=1
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 338618 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x7fa150000990
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 7fa164139c90 thread_stack 0x40000
/usr/sbin/mysqld(my_print_stacktrace+0x29)[0x77b8b9]
/usr/sbin/mysqld(handle_fatal_signal+0x471)[0x6790e1]
/lib64/libpthread.so.0(+0xfcd0)[0x7fa16871ccd0]
/lib64/libc.so.6(gsignal+0x35)[0x7fa166912395]
/lib64/libc.so.6(abort+0x148)[0x7fa1669138a8]
/lib64/libc.so.6(+0x74045)[0x7fa166951045]
/lib64/libc.so.6(+0x79df6)[0x7fa166956df6]
/usr/sbin/mysqld(free_root+0x3d)[0x771f3d]
/usr/sbin/mysqld(free_defaults+0x4c)[0x7645dc]
/usr/sbin/mysqld(mysql_read_default_options+0x10a)[0x65d3ca]
/usr/sbin/mysqld(mysql_init+0xb5)[0x65df35]
/usr/sbin/mysqld(handle_slave_io+0x59f)[0x543aef]
/lib64/libpthread.so.0(+0x8034)[0x7fa168715034]
/lib64/libc.so.6(clone+0x6d)[0x7fa1669c57ad]

Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (0): is an invalid pointer
Connection ID (thread ID): 4
Status: NOT_KILLED

You may download the Percona Server operations manual by visiting
http://www.percona.com/software/percona-server/. You may find information
in the manual which will help you identify the cause of the crash.

this simple fix makes it not to crash:
# chgrp mysql /etc/mysql/delfiua.conf