Package: openrc
Version: 0.21-1
Severity: important
Hi
openrc's behaviour of closing fd 0,1,2 can potentially break daemons. An
example of this was found with dbus 1.10.6-1ubuntu3 on ubuntuBSD (however the
openrc version this report is based on, is imported pristine from Debian).
Below are excerpts from ktrace/kdump output of dbus-daemon (when being called
by openrc).
First a socket is created and assigned fd 0 because it's the first free fd:
1057 dbus-daemon CALL socket(PF_LOCAL,SOCK_CLOEXEC|SOCK_STREAM,0)
1057 dbus-daemon RET socket 0
1057 dbus-daemon CALL stat(0x635520,0x7fffffffe480)
1057 dbus-daemon NAMI "/var/run/dbus/system_bus_socket"
1057 dbus-daemon RET stat -1 errno 2 No such file or directory
1057 dbus-daemon CALL bind(0,0x7fffffffe520,0x21)
1057 dbus-daemon STRU struct sockaddr { AF_LOCAL,
/var/run/dbus/system_bus_socket }
1057 dbus-daemon NAMI "/var/run/dbus/system_bus_socket"
1057 dbus-daemon RET bind 0
1057 dbus-daemon CALL listen(0,0x1e)
1057 dbus-daemon RET listen 0
1057 dbus-daemon CALL fcntl(0,F_GETFL,0)
1057 dbus-daemon RET fcntl 2
1057 dbus-daemon CALL fcntl(0,F_SETFL,0x6<O_RDWR|O_NONBLOCK>)
1057 dbus-daemon RET fcntl 0
1057 dbus-daemon CALL
chmod(0x635520,0x1ff<S_IRUSR|S_IWUSR|S_IXUSR|S_IRGRP|S_IWGRP|S_IXGRP|S_IROTH|S_IWOTH|S_IXOTH>)
1057 dbus-daemon NAMI "/var/run/dbus/system_bus_socket"
1057 dbus-daemon RET chmod 0
then another routine in dbus closes fds 0,1,2, replacing them with /dev/null
descriptors. Obviously it intends to disable stdio however unknowingly it is
actually closing the socket:
1058 dbus-daemon CALL open(0x427733,0x2<O_RDWR>,<unused>0)
1058 dbus-daemon NAMI "/dev/null"
1058 dbus-daemon RET open 3
1058 dbus-daemon CALL dup2(0x3,0)
1058 dbus-daemon RET dup2 0
1058 dbus-daemon CALL dup2(0x3,0x1)
1058 dbus-daemon RET dup2 1
1058 dbus-daemon CALL issetugid
1058 dbus-daemon RET issetugid 0
1058 dbus-daemon CALL dup2(0x3,0x2)
1058 dbus-daemon RET dup2 2
1058 dbus-daemon CALL close(0x3)
1058 dbus-daemon RET close 0
then operations on the socket fail, leaving the system with a broken dbus:
1058 dbus-daemon CALL accept4(0,0x7fffffffe5b0,0x7fffffffe5ac,0x10000000)
1058 dbus-daemon RET accept4 -1 errno 38 Socket operation on non-socket
1058 dbus-daemon CALL fcntl(0xffffffff,F_GETFD,0)
1058 dbus-daemon RET fcntl -1 errno 9 Bad file descriptor
If you want to disable stdio I think it would be much better to replace them
with /dev/null descriptors. Too many apps assume fds 0,1,2 are reserved for
stdio. Leaving them free for any other use is dangerous IMHO.
--
Jon Boden
ubuntuBSD -- The power of FreeBSD kernel with familiarity of Ubuntu OS!
http://www.ubuntubsd.org/ -- https://twitter.com/ubuntuBSD
