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SubjectRe: [patch] NE2000
Andrew Morton wrote:
>
> Jorge Nerin wrote:
> >
> > ...
> > So I think that it could be a little window near sock_wait_for_wmem that
> > could be SMP insecure wich is affecting me.
> >
> > The code of sock_wait_for_wmem in 2.4.0-test10 is this:
> >
> > static long sock_wait_for_wmem(struct sock * sk, long timeo)
> > {
> > DECLARE_WAITQUEUE(wait, current);
> >
> > clear_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);
> > add_wait_queue(sk->sleep, &wait);
> > for (;;) {
> > if (signal_pending(current))
> > break;
> > set_bit(SOCK_NOSPACE, &sk->socket->flags);
> > set_current_state(TASK_INTERRUPTIBLE);
> > if (atomic_read(&sk->wmem_alloc) < sk->sndbuf)
> > break;
> > if (sk->shutdown & SEND_SHUTDOWN)
> > break;
> > if (sk->err)
> > break;
> > timeo = schedule_timeout(timeo);
> > }
> > __set_current_state(TASK_RUNNING);
> > remove_wait_queue(sk->sleep, &wait);
> > return timeo;
> > }
> >
> > Does someone see something SMP insecure? Perhaps I'm totally wrong, this
> > could also be somewhere in the interrupt handling, don't know.
>
> No, that code is correct, provided (current->state == TASK_RUNNING)
> on entry. If it isn't, there's a race window which can cause
> lost wakeups. As a check you could add:
>
> if ((current->state & (TASK_INTERRUPTIBLE|TASK_UNINTERRUPTIBLE)) == 0)
> BUG();
>
> to the start of this function.

OK, added, the function now looks like this:

static long sock_wait_for_wmem(struct sock * sk, long timeo)
{
DECLARE_WAITQUEUE(wait, current);

if ((current->state & (TASK_INTERRUPTIBLE|TASK_UNINTERRUPTIBLE))
== 0)
BUG();

clear_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);
add_wait_queue(sk->sleep, &wait);
for (;;) {
if (signal_pending(current))
break;
set_bit(SOCK_NOSPACE, &sk->socket->flags);
set_current_state(TASK_INTERRUPTIBLE);
if (atomic_read(&sk->wmem_alloc) < sk->sndbuf)
break;
if (sk->shutdown & SEND_SHUTDOWN)
break;
if (sk->err)
break;
timeo = schedule_timeout(timeo);
}
__set_current_state(TASK_RUNNING);
remove_wait_queue(sk->sleep, &wait);
return timeo;
}

I have to put it _after_ DECLARE_WAITQUEUE in order to compile, if I put
it before it says me that wait is undeclared :-?

Well recompile, reboot, and got caugth by BUG(), after some tests.

[root@quartz ~]# ping -f -s 15000 pp_head
PING pp_head.pp.redvip.net (192.168.1.20) from 192.168.1.3 :
15000(15028) bytes of data.
..............invalid operand: 0000
CPU: 0
EIP: 0010:[<c0195b30>]
EFLAGS: 00010296
eax: 0000001a ebx: c2604000 ecx: c021e2e8 edx: c0266440
esi: c26eeba0 edi: c26eeba0 ebp: 7fffffff esp: c2605c88
ds: 0018 es: 0018 ss: 0018
Process ping (pid: 2202, stackpage=c2605000)
Stack: c02047a5 c02049eb 000002d2 7fffffff c26eeba0 c2604000 00000000
c26c4024
01234567 c2604000 00000000 00000000 01234567 c2604000 00000000
00000000
c0195c99 c26eeba0 7fffffff c26c4024 c264d0c0 c26c4010 000005dc
00000000
Call Trace: [<c02047a5>] [<c02049eb>] [<c0195c99>] [<c01aa692>]
[<c01aaa1e>] [<c01c0180>] [<c01c04de>]
[<c01c0180>] [<c01c6f48>] [<c01c6f86>] [<c0192fad>] [<c01c6f48>]
[<c01941b8>] [<c0193ee6>] [<c0165c9a>]
[<c016e602>] [<c01945fc>] [<c0109477>]
Code: 0f 0b 83 c4 0c 8b 87 50 03 00 00 f0 0f ba 70 04 00 8d 4c 24
Violación de segmento
[root@quartz ~]#


Nov 6 12:00:07 quartz kernel: kernel BUG at sock.c:722!
Nov 6 12:00:07 quartz kernel: invalid operand: 0000
Nov 6 12:00:07 quartz kernel: CPU: 0
Nov 6 12:00:07 quartz kernel: EIP: 0010:[sock_wait_for_wmem+104/244]
Nov 6 12:00:07 quartz kernel: EFLAGS: 00010296
Nov 6 12:00:07 quartz kernel: eax: 0000001a ebx: c2604000 ecx:
c021e2e8 edx: c0266440
Nov 6 12:00:07 quartz kernel: esi: c26eeba0 edi: c26eeba0 ebp:
7fffffff esp: c2605c88
Nov 6 12:00:07 quartz kernel: ds: 0018 es: 0018 ss: 0018
Nov 6 12:00:07 quartz kernel: Process ping (pid: 2202,
stackpage=c2605000)
Nov 6 12:00:07 quartz kernel: Stack: c02047a5 c02049eb 000002d2
7fffffff c26eeba0 c2604000 00000000 c26c4024
Nov 6 12:00:07 quartz kernel: 01234567 c2604000 00000000
00000000 01234567 c2604000 00000000 00000000
Nov 6 12:00:07 quartz kernel: c0195c99 c26eeba0 7fffffff
c26c4024 c264d0c0 c26c4010 000005dc 00000000
Nov 6 12:00:07 quartz kernel: Call Trace: [vga_con+2501/10176]
[vga_con+3083/10176] [sock_alloc_send_skb+221/300]
[ip_build_xmit_slow+378/1208] [ip_build_xmit+78/816] [raw_getfrag+0/36]
[raw_sendmsg+642/752]
Nov 6 12:00:07 quartz kernel: [raw_getfrag+0/36]
[inet_sendmsg+0/68] [inet_sendmsg+62/68] [sock_sendmsg+129/164]
[inet_sendmsg+0/68] [sys_sendmsg+380/464] [sys_recvfrom+238/256]
[set_cursor+110/132]
Nov 6 12:00:07 quartz kernel: [write_chan+462/488]
[sys_socketcall+460/484] [system_call+55/64]
Nov 6 12:00:07 quartz kernel: Code: 0f 0b 83 c4 0c 8b 87 50 03 00 00 f0
0f ba 70 04 00 8d 4c 24

Nov 6 12:06:11 quartz kernel: kernel BUG at sock.c:722!
Nov 6 12:06:11 quartz kernel: invalid operand: 0000
Nov 6 12:06:11 quartz kernel: CPU: 1
Nov 6 12:06:11 quartz kernel: EIP: 0010:[sock_wait_for_wmem+104/244]
Nov 6 12:06:11 quartz kernel: EFLAGS: 00010296
Nov 6 12:06:11 quartz kernel: eax: 0000001a ebx: c1f54000 ecx:
c021e2e8 edx: c0266440
Nov 6 12:06:11 quartz kernel: esi: c3cd6100 edi: c3cd6100 ebp:
7fffffff esp: c1f55c88
Nov 6 12:06:11 quartz kernel: ds: 0018 es: 0018 ss: 0018
Nov 6 12:06:11 quartz kernel: Process ping (pid: 2993,
stackpage=c1f55000)
Nov 6 12:06:11 quartz kernel: Stack: c02047a5 c02049eb 000002d2
7fffffff c3cd6100 c1f54000 00000000 c2648824
Nov 6 12:06:11 quartz kernel: 01234567 c1f54000 00000000
00000000 01234567 c1f54000 00000000 00000000
Nov 6 12:06:11 quartz kernel: c0195c99 c3cd6100 7fffffff
c2648824 c260c2c0 c2648810 000005dc 00000000
Nov 6 12:06:11 quartz kernel: Call Trace: [vga_con+2501/10176]
[vga_con+3083/10176] [sock_alloc_send_skb+221/300]
[ip_build_xmit_slow+378/1208] [ip_build_xmit+78/816] [raw_getfrag+0/36]
[raw_sendmsg+642/752]
Nov 6 12:06:11 quartz kernel: [raw_getfrag+0/36]
[inet_sendmsg+0/68] [inet_sendmsg+62/68] [sock_sendmsg+129/164]
[inet_sendmsg+0/68] [sys_sendmsg+380/464] [sys_recvfrom+238/256]
[set_cursor+110/132]
Nov 6 12:06:11 quartz kernel: [write_chan+462/488]
[sys_socketcall+460/484] [system_call+55/64]
Nov 6 12:06:11 quartz kernel: Code: 0f 0b 83 c4 0c 8b 87 50 03 00 00 f0
0f ba 70 04 00 8d 4c 24
Nov 6 12:06:11 quartz kernel: NET: 6 messages suppressed.
Nov 6 12:06:11 quartz kernel: NAT: 0 dropping untracked packet c26984a0
1 192.168.1.20 -> 192.168.1.3
Nov 6 12:06:11 quartz kernel: NAT: 0 dropping untracked packet c2828a80
1 192.168.1.20 -> 192.168.1.3
Nov 6 12:06:11 quartz kernel: NAT: 0 dropping untracked packet c265d560
1 192.168.1.20 -> 192.168.1.3
Nov 6 12:06:11 quartz kernel: NAT: 0 dropping untracked packet c2828a80
1 192.168.1.20 -> 192.168.1.3
Nov 6 12:06:11 quartz kernel: NAT: 0 dropping untracked packet c53bc820
1 192.168.1.20 -> 192.168.1.3
Nov 6 12:06:11 quartz kernel: NAT: 0 dropping untracked packet c264d780
1 192.168.1.20 -> 192.168.1.3
Nov 6 12:06:41 quartz kernel: kernel BUG at sock.c:722!
Nov 6 12:06:41 quartz kernel: invalid operand: 0000
Nov 6 12:06:41 quartz kernel: CPU: 1
Nov 6 12:06:41 quartz kernel: EIP: 0010:[sock_wait_for_wmem+104/244]
Nov 6 12:06:41 quartz kernel: EFLAGS: 00010296
Nov 6 12:06:41 quartz kernel: eax: 0000001a ebx: c1f54000 ecx:
c021e2e8 edx: c0266440
Nov 6 12:06:41 quartz kernel: esi: c3cd6800 edi: c3cd6800 ebp:
7fffffff esp: c1f55c88
Nov 6 12:06:41 quartz kernel: ds: 0018 es: 0018 ss: 0018
Nov 6 12:06:41 quartz kernel: Process ping (pid: 2994,
stackpage=c1f55000)
Nov 6 12:06:41 quartz kernel: Stack: c02047a5 c02049eb 000002d2
7fffffff c3cd6800 c1f54000 00000000 c2644824
Nov 6 12:06:41 quartz kernel: 01234567 c1f54000 00000000
00000000 01234567 c1f54000 00000000 00000000
Nov 6 12:06:41 quartz kernel: c0195c99 c3cd6800 7fffffff
c2644824 c5b8be60 c2644810 000005dc 00000000
Nov 6 12:06:41 quartz kernel: Call Trace: [vga_con+2501/10176]
[vga_con+3083/10176] [sock_alloc_send_skb+221/300]
[ip_build_xmit_slow+378/1208] [ip_build_xmit+78/816] [raw_getfrag+0/36]
[raw_sendmsg+642/752]
Nov 6 12:06:41 quartz kernel: [raw_getfrag+0/36]
[inet_sendmsg+0/68] [inet_sendmsg+62/68] [sock_sendmsg+129/164]
[inet_sendmsg+0/68] [sys_sendmsg+380/464] [sys_recvfrom+238/256]
[kfree_skbmem+40/140]
Nov 6 12:06:41 quartz kernel: [__kfree_skb+369/376]
[nfsd:__insmod_nfsd_O/lib/modules/2.4.0-test10-ne2k/kernel/fs/nfs+-289558/96]
[nfsd:__insmod_nfsd_O/lib/modules/2.4.0-test10-ne2k/kernel/fs/nfs+-288860/96]
[qdisc_restart+108/376] [net_tx_action+194/300] [sys_socketcall+460/484]
[system_call+55/64]
Nov 6 12:06:41 quartz kernel: Code: 0f 0b 83 c4 0c 8b 87 50 03 00 00 f0
0f ba 70 04 00 8d 4c 24

Sorry, I can't pass it througth ksymoops because it doesn't work for me
in later kernels (RH 6.9.5) it says Fatal Error (re_compile) - Invalid
range end, and I have recompiled it. So I have to give you the results
of sysklogd.

As a side note I have to say that after those BUG the net is still
working, and I have those rules added in init scripts:
modprobe -k ip_tables
modprobe -k iptable_nat
insmod -k ipt_MASQUERADE
iptables -t nat -A POSTROUTING -o ppp+ -j MASQUERADE
iptables -A FORWARD -i ppp+ -m state --state RELATED,ESTABLISHED
-j ACCEPT
iptables -A FORWARD -o ppp+ -j ACCEPT
echo 0 >/proc/sys/net/ipv4/tcp_ecn
Under heavy packet load in these tests I see that NAT messages about
dropped packets.

More tests as requested.

--
Jorge Nerin
<comandante@zaralinux.com>
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