Recent full disclosure post - Local DOS

[John Baldwin]

On Friday, January 28, 2011 11:08:37 am Tom Judge wrote:
> On 01/28/2011 08:29 AM, Tom Judge wrote:
> > 
> > Has anyone looked at this:
> > 
> > [Full-disclosure] FreeBSD local denial of service - forced reboot
> > 
> > http://lists.grok.org.uk/pipermail/full-disclosure/2011-
January/078836.html
> > 
> 
> I have done some simple tests on ESXi 4.1.0, 260247.
> 
> releng/8.1 - i386 - Not repeatable.
> 
> releng/8.2-RC1 - amd64 - Not repeatable.
> 
> 
> current 9.0-CURRENT-201011 - i386 - Repeatable:
> 
> Unread portion of the kernel message buffer:
> panic: tcp_output: mbuf chain shorter than expected
> cpuid = 0
> KDB: enter: panic
> Physical memory: 239 MB
> Dumping 99 MB: 84 68 52 36 20 4
> 
> 
> (kgdb) bt
> #0  doadump () at pcpu.h:231
> #1  0xc04d5809 in db_fncall (dummy1=1, dummy2=0, dummy3=-1057111072,
> dummy4=0xcd0cc78c "") at /usr/src/sys/ddb/db_command.c:548
> #2  0xc04d5c01 in db_command (last_cmdp=0xc0e0e27c, cmd_table=0x0,
> dopager=1) at /usr/src/sys/ddb/db_command.c:445
> #3  0xc04d5d5a in db_command_loop () at /usr/src/sys/ddb/db_command.c:498
> #4  0xc04d7c7d in db_trap (type=3, code=0) at /usr/src/sys/ddb/db_main.c:229
> #5  0xc08ee99e in kdb_trap (type=3, code=0, tf=0xcd0cc930) at
> /usr/src/sys/kern/subr_kdb.c:546
> #6  0xc0bfcf5b in trap (frame=0xcd0cc930) at
> /usr/src/sys/i386/i386/trap.c:732
> #7  0xc0be5e8c in calltrap () at /usr/src/sys/i386/i386/exception.s:168
> #8  0xc08eeb6a in kdb_enter (why=0xc0cddbdf "panic", msg=0xc0cddbdf
> "panic") at cpufunc.h:71
> #9  0xc08bba04 in panic (fmt=0xc0cfb014 "%s: mbuf chain shorter than
> expected") at /usr/src/sys/kern/kern_shutdown.c:574
> #10 0xc0a3ecc6 in tcp_output (tp=0xc2789768) at
> /usr/src/sys/netinet/tcp_output.c:1084
> #11 0xc0a4a309 in tcp_ctloutput (so=0xc3a179a8, sopt=0xcd0ccc0c) at
> /usr/src/sys/netinet/tcp_usrreq.c:1328
> #12 0xc092742d in sosetopt (so=0xc3a179a8, sopt=0xcd0ccc0c) at
> /usr/src/sys/kern/uipc_socket.c:2396
> #13 0xc092ec95 in kern_setsockopt (td=0xc33b1b40, s=4, level=6, name=4,
> val=0xbfbfdacc, valseg=UIO_USERSPACE, valsize=4) at

This is an IPPROTO_TCP, TCP_NOPUSH with an optval of 0.

Can you try making a far simpler program that just does:

	int optval, s;

	s = socket(PF_INET, SOCK_STREAM, 0);
	if (s < 0)
		err(1, "socket");
	optval = 0;
	if (setsockopt(s, IPPROTO_TCP, TCP_NOPUSH, &optval, sizeof(optval)) < 0)
		err(1, "setsockopt");

and see if that breaks?

-- 
John Baldwin